From what I've heard, and this is all hearsay, soon LL will be stopping all viewers based off of V1 and only allow V2 based viewers to work on the grid. This worries me. We may be forced to use V2 or a clone of it with that nasty sidebar and all the other irritating new 'features'.
Most of the people I run into don't use V2 and I mean anywhere I go. Mass majority use Phoenix (you would think LL would catch on to the hint here, people don't like V2!) Seriously, go to any club or other Sim where there are a lot of avatars and look at your radar. You'll find that very very few use the V2.
Now, I understand the need for a new viewer, all the advances and new things in SL like alphas and physics, and the new mesh (something I don't quite understand yet) have just been patched into the old viewer. With V2 it's not a patch, it's built that way which means smoother operation and less bugs. I don't want LL to get rid of V2, I just want a choice. I want to be able to play how I want to with the UI I find appealing. If people like the new UI that's great, (just from looking around I don't think they do)but give those of us that have been playing for a long time the choice to keep our nice friendly UI.