My 9700 still has the stock .330 OS. I've been so tempted to try another build, but in the end decided not to for a couple reasons. First off, it's almost universally accepted that .330 wins on battery. Anything newer isn't as good, it seems, and this is important to me. Secondly, it starts a slippery slope- I install one OS, and am either happy or not. Then the next latest and greatest comes out... should I go with that one now? Or hold out? Where does it end? Lastly, I'm in a unique position where I've been carrying around the same working TCP/IP service books for the past few phones, and I don't want to risk botching the working internet-without-data-plan I have by wiping my phone.
But if you're bored, or don't mind experimenting, or are just a techie who wants the latest thing, by all means try one out. There's a lot of hubbub about the latest .536 leak, and most of the reviews are positive. Just don't expect it to cure cancer or solve world hunger; we're talking about unnamed tweaks and bug fixes, not a major upgrade. There's a reason these builds are 5.0.0.x, not 5.1 or even 5.0.1. The biggest "features" I see praise for are that the browser (may or may not) be
almost two seconds faster on loading, bootup time (in some cases)
might be a minute less than what it was, the lock and mute buttons are changed (which some people hate, and others love), and the thumbnail image previews load quicker (though may be pixelated)
And as always take everything you read with a grain of salt, because as with any computer, one out of every so many upgrades will be done wrong, or have errors, or random glitches which don't reflect the actual overall software... and conversely, freshly reinstalling any OS tends to make things snappier and run quicker.