Mesa 7.3 was released back in January and was branched from the master Git tree so that it can be stabilized further and go on to form Mesa 7.4. Well, nearly three months later, Mesa 7.4 is getting close to being released...
The latter works (NVidia's one only) while the former is still broken as crap.
I had a lovely supper and a piece of halibut that was good enough for Jehovah. Oh, wait, that's off topic as well. :-)
Anyways, you should have known that the only drivers which support nVidia-hardware completely are closed source. So if you want to use open source only, don't buy their products. I personally don't think that some possibly broken mesa driver is the only problem you face when you use open source drivers for nVidia. In fact I do even believe that it's the least significant one.
Using mesa 7.4 I get lots of display errors. They apparently have been there since I first tested the 7.4 branch and could be related to KMS/DRI2.
Hmm, after updating compiz (= rebuilding it) those problems seem to be gone.