I have used this firmware version for a day and these are my observations:
1) Earphone Volume is as low as, if not lower than the volume in JB2(damn you Samsung
, how am I expected to listen to music on the Metro)
2) Battery holds up as good as IK4 for me i.e. around 60% after a day of moderate use(few calls, 1hr music, checking mail on edge)
3) Lock button is good(not much difference from JB2)
4) Available Memory 27MB (when idle with 2 widgets active(Digi Clock, Pure Grid Calendar))
5) General Usability: Slow, sluggish response to touchscreen (It wouldn't be an official Samsung Galaxy firmware if it did not display this unique trait, which has been a hallmark of all official f/ws till date
). However it is better than JB2 in this aspect. I haven't used the Market app as of now, however judging from my experience with the browser I expect it to perform as bad as in JB2.
6) Haven't come across the no sleep problem, but I have not used Location Services as of now.