Jane:
The transition tends to move back and forth for most people before taking hold, but even so the state of equanimity is not particularly stable, especially if you lose momentum in your practice because you're feeling good.
I can relate to this. I went through a hellish DN on retreat and ended in EQ. I slipped back many times over the next few weeks and it was a bit of a slog to get up to EQ each sit. For me the emotional side was minimally noticed - some anger, short-temperedness and some recurrence of old stress symptoms. My DN's consist mostly of unpleasant sensations and tension headaches.
The DN seems to break either over the course of 5-10secs during a sit, or between sits. Many times on retreat I got up when the gong went with crushing headaches, pain, tension, itching from Reobservation only to find I'd waltz straight into peaceful vibrations much as Jane described above when I lay in my room to continue just minutes later.
At home EQ seems to have pretty much stuck for now. Though I did dip back to A&P and up through the DN just a few days ago. The sensations were known, expected and held little fear. Because of that (educated guess) they were mild and quickly over.
The trick? For me it was "melting into" the nasty sensations. Allowing them to be what they were and almost enjoying the experience. Accepting what it was and trying to learn as much as I could from some pretty rich sensations! The pain comes from aversion, so if you can turn that right around, you move into EQ --at least in my experience. Though this seems to match up with what others have reported and what I've read in MCTB.