One of the characteristics of this new territory is that I feel alot more compassion and empathy for people (not in a condescending way)
Yes: empathy/understanding is much more likely to come up on its own after stream-entry: this mind is a little less occluded a little less of the time by its own perseverations and further one has a direct understanding of why people/animals may be acting harshly. Yet, looking at the fetters still attached to a stream enterer...not so pretty ;)
You may already be considering this, but I regularly support and re-interate the consideration of about nine months to a year timeline of significant changes following stream entry. Everyone is perhaps somewhat different, but I found this metric very true: there were smaller significant shifts practically every three months.
So Metta practice is useful at this stage you are suggesting?
I am being waaaay more emphatic than "suggesting". I am being very clear here: one will see where one has a friendliness, metta, and where one has not. One will be worked by metta through and through. Stream-entry has its own dissatisfaction or everyone would stop here, and that dissatisfaction collects around what is non-metta and when/where/why one is emitting/responding from non-metta/ where one has aversion or hostility. Perhaps that sounds harsh. But it's natural; one is just learning. One has to learn by daily experience where there is arising from the mind that which is not metta, friendliness, or arising aversion/hostility. [Unless one manages to shoot straight to equanimity and I guess fourth path? I wouldn't know anything about these later changes.]
For instance, perhaps you now know that for all one reads about stream entry, the actual mental shift cannot really be anticipated nor imagined the way it actually happens. The way metta actually happens can seems like something completely unexpected and unforeseen and unimaginable. This is normal. If you have a mentor in this area, a teacher in any field who you know is just "safe", "soft", platonically attractive to be around it will be good to surround oneself with the memory or knowledge of that mentor-- constantly take in how they are doing things, how they are talking to others, how they are walking about.
If you look at the fetter model, the same two fetters follow the two middle "paths". Metta addresses both paths' fetters (their fetters are the same, differing in severity).
I am interested in your 'faith' comment - could you expand on this a little?
There are a few translations of Vicikicchā.
After stream entry I was not looking for the fetters or what had fallen away. By nine months after, though, I could look back and see how Vicikicchā panned out for this brain anyway. From months 3-6 after stream-entry I was just magnetized to one of my dharma teachers and pali scriptures-- as if the mind fell devotedly for the means that had "saved" it/"released" it into that initial "path". I could see myself going through all sorts of sincere devotional gestures and action week after week.
Around month 5-8 "faith" moved into more of the translation "skeptical doubt"-- as in the disappearance of skeptical doubt. Faith (development of) and skeptical doubt (release of) are two renderings, I think, of Vicikicchā.
Lastly, I think my mind just opened (and I consider that it was very open before) and suddenly I found I had a lot more "I don't know: just observe"-- that I did not have so many answers nor need to make any up. The mind of "don't know, just observe" is very expansive and sheds a lot of urge to be conclusive or containing. There is little urge to take a position outside of curiosity and observation and some kind of metta-receptivity. And skeptical doubt at the very least is an assertion which has an urge to negate, even subtly, as in condescension (which condescension is a hallmark of souring equanimity, in my view). There is a world of difference between observing receptively/openly and asserting skepticism --- needing to assert skepticism***. Does this make any sense?
[edits: typos]
[***this is not the same as asserting practical doubt, like if someone tells me a peanut is a cashew-- there I would have very practical doubt.]