I still find a number of things problematic, but it has improved (particularly stability, as the initial Viewer2.0 crashed a lot for me). I do like a lot of the features, and as a slow adopter, I am still learning to make full use of these.
I think that the feature I most need in Viewer2 (and the only "make or break" feature for me at the moment), is the patch made by Sione, that allows an end user to detect (and choose to block) attempts to target media streams at them. Without this feature, I am forced to turn off media features if I want to have control over my privacy and real life data (such as IP), while using SL.
A setting that allows me to choose to block cookies from anyone but Secondlife/Linden Lab would be good too, so I can use search and retain control over my privacy.