My nose is weird. There is always one nostril where there are like no sensations at all or if there are some, they are very weak. Sometimes it's the right nostril, sometimes the left. So I tend to focus on only one nostril at a time nowadays. Is there any drawback with this compared to focusing on both? Will it lead to energetic imbalances or something like that? 
Still no jhana. There are big gaps between breaths sometimes with almost no sensation at the nose so thoughts pop up easily, if that matters. It's not like they distract me from the breath.

This is perfectly normal. If you check on a full day, you'll find out that there is a nostril much more fully opened than the other one, and it changes every 1.5 hour or so (each of us has its own time pattern).

Open left nostril : moon, cooling energy. You are in a yin, more passive and receptive state. The parasympathetic nervous system is active.
Open right nostril : sun, active energy. You are in a yang, more alert and energic state. The sympathetic nervous system is active.

So I don't know if it would lead to energetic imbalances, but it can be interesting to see how it impacts your sit depending on which nostril is "active" at the time.

For me when practicing concentration, there is no need to bother about which or which nostril is more felt. The sensation at the tip of the nose soon becomes much more a mental object than a truly physical perception.

That can explain things. Todays 40-min sit was full of thoughts flowing like a loud river, spontaneous movements and unusual breathing patterns. The left nostril was "active".
But I don't feel distracted by the thoughts, I'm still aware of the breath.

You havent noticed the same with your eyes? I can feel them switching priority when i meditate it can be a little distracting.
When it comes to nostrils i only got one that is fully open, the nosebone is bent for me, so everynow and then i basically only have one path. Not getting enough air really pulls one out of the zone

Is that a focus / re-focus feeling, or an actual physical eyes thing ?
Because I experience it as moving energetic moiré but I'm not sur we're talking about the same thing.

Goenka has us focus on the space right beneath the nostrals, above the upper lip line.  There you get sensations of air movement whichever combination of nostrils is operating.  This focus helps us focus more on actual present moment sensations and less time wonding what's going on.

After a few days on retreat doing exclusivily awareness of that area, I can now usually feel the sensations at that spot that are distinct from the feelings associated with air movement, pulse being the easiest to feel, but also some kind of vauge tension or temperature or subtle vibrations.

In response to the other poster, recently I've become aware of the fact that the sensations and effects of increasing concentration occur to different degrees in the left half of my brain and the right half of my brain, which includes sensations that come in the optical nerve.  I gather this is common.

Of course, from the insight point of view, all this phenomonology is irrelevent, only the awareness of the sensations is important.

It feels physical, switches like a pulsewave, pressure of sorts that move between the eyeballs. Pressure decrease in one and increase in the other, back and forth. Ive interpreted it as a eye focus priority switch.

You know what, guys, I think these problems, specifically, are what help us figure out this "insight" stuff.  The jhanas arise from suffering itself, for me.  Or maybe I should say, they arise in spite of suffering. It's when I see that I don't need to do anything about anything that my mind lets go and "gives up" in a majestic flood of piti and sukha.

When you're annoyed like this, see if you can't just let the annoyance happen without trying to fix it. The frustration comes from wanting to do something - wanting to make everything perfect, wanting to create the conditions where everything is exactly right. But this never happens. There's always something wrong.

The goal is not to resolve everything, the goal is to drop the need for resolution. The result is the same both ways. You know when you kind of forget about yourself - everything is going right, you're having a good time, you're relaxed. See if you can't do that with nasal annoyances too, or with negative feelings.  Y ou don't have to be having a good time, but you can move into that mind-frame where you're not really trying or checking up on yourself.  Just let go of the part of you that keeps track of things - the part that is monitoring and holding things together...the part that is, at this moment, trying to modify experience and make it perfect. You can be in any emotional state and have any kind of physical annoyance be hapening and still get into jhana. Think of it like getting lost in the moment. You can't get lost while trying to make everything just right. Ignore yourself. Forget yourself.

And then what?

Totally agree. I had a lot of stuff bothering me before, there are still there but I don't give a s*** anymore and jhana is closer to rise than ever.

Still I think that there are layers upon layers of ever subtler stuff to deal with, but you've described quite accurately the big picture.

re: Pål (1/18/15 3:46 PM )
"My nose is weird. There is always one nostril where there are like no sensations at all or if there are some, they are very weak. Sometimes it's the right nostril, sometimes the left."

(Expanding on what Jean B. offered.) Your nose could well be quite normal, physiologically. One manifestation of natural bodily rhythms is this shift between sides of the nose. These 'intra-circadian' rhythms – popularized many years ago as (seriously over-simplifed, pseudo-scientific) "biorhythms" – are natural interdiurnal ('within the day,' as distinct from the grosser circadian rhythm of day and night) fluctuations in things like body temperature, mental alertness, and this shift of clearness on one side and stuffiness on the other in the nostrils. The period of these fluctuations, sort of wave-forms, varies, but runs on average in the neighborhood of about 90 minutes.This is perhaps most easily noticeable in the way one feels mentally alert and keen at one time, and then, an hour to two later, s/w foggy and sleepy. It's subtle but discernable.

These can be useful to notice, as one would not expect to be more or less productive at different phases of these cycles. When 'sloth and torpor' seem to be strong, one can do things productive that don't require great energy. At the opposite phases is the time to energetically push all-out.

"So I tend to focus on only one nostril at a time nowadays."

As I recall, the meditation instruction is to focus on the sensation, or feeling of touch at the nostril(s), rather than on the nostril per se. In advanced teachings (e.g. Abhidhamma and commentaries), touch is special among the 5 physical sense modalities: It is the only sense that doesn't consist simply or exclusively of apprehending an external influence (such as light, sound, smell or taste of something from the outside). It is more the body feeling itself in response to contact with something external, but can also be internal. 'Proprioception', the body's sense of its own position or motion, is a case in point. Also, the touch dhātuis unique in that it involves the three 'primary' or 'great elements' (mahā-bhūta) of earth (substance), air (motion, support) and fire (temperature), but not water (cohesion, fluidity).

"There are big gaps between breaths sometimes with almost no sensation at the nose so thoughts pop up easily, if that matters."

Try breathing smoothly and continuously, even to the point where there seems no switch between in and out phases. That makes for a more static object, which more easily triggers the mental nimitta ('reflex-image'), which is what the mind, eventually, actually absorbs into. At least, if you're looking for 'hard' jhana (full absorption).

if you can later change the flow at will, then you are not far from opening central channel and from there even subtle channel.
when you open central channel you can enjoy flow from both nostrils at the same time.

This morning the left nostril was "active". There were no spontaneous movements and concentration was pretty smooth sometimes.

"As I recall, the meditation instruction is to focus on the sensation, or feeling of touch at the nostril(s), rather than on the nostril per se."

In the suttas, it's neither. But yes ofc I mean sensations rather than the nostril itself, since the nose is a mental object and can't be percieved through the sense of touch, as I see it.