You'll find almost as many different opinions on this topic as there are BB users. There's actually a discussion going on about this now in this thread.
I had decent luck with .540. The OS was very stable and I had no issues; battery life was ok, but not spectacular. Sometimes I can go for stretches at home on WiFi and have battery drain as low as 1.2% per hour for an entire weekend (very good), while some days at work with only at&t's crappy signal and no WiFi the drain would be 7% or more per hour with low to moderate usage (ok, not great), sometimes depending on where I physically was in the building. I just loaded up .585 with the .540 radio file (see how to do that here -- look for Phill_UK's post #19), so we'll see how that goes over the next few days.
how do you rate battery life and overall build stability.
Well its only two days, but I would rate the battery life as great compared to other builds, however I have not used it on regular day for me, I was um sick on Friday (ehem, cough cough!!!) seems stable, but there seems to be some reports of minor issues.
@byul,
thank you very much...
..
downloading...
i didn't a CD with 9900 retail version
and i have DM v5.0 installed.. is it fine if i update 9900 with it.