I updated and like some of the new features but I'm also waiting for Adobe to make good on the promise of 4.0.
I hope that cs6 is released now Adobe will spend more resources on LR again - even the sdk isn't released yet, and the performance problems affect me, too. But having said this, I'd advise anyone to upgrade nevertheless since the 2012 raw process is at least as powerful as the 2010 one and much quicker once you get used to it. Shame auto-tone is still broken with PV2012...
The ability to process HDR TIFF files. (16, 24 or 32-bit TIFF files)
Doh - this is non-working, nice try, Adobe - another feature introduced w/o testing in RC, and broken again. Now you can adjust the exposure from -10 to +10 (instead of -5 to +5 before), but that's not enough! I'd rather stick with Photomatrix and the like for the time being which is necessary to assemble a hdr file anyway.