argument defaults and validation; pluggable. This will greatly ease some of the problems with argument discovery. We need to get a few more basic plugins written for this, but basically with a little bit of code you can do all kinds of cool stuff with arguments not there or not matching what you want.
Quick links on the edit page; hover links on the view view page.
A weak but expandable view analyzer tool
Revamped view list page, plus the first advanced help file!
#248999: (by eaton) Grid style that uses a simple table to display a grid in X columns.
A theme information tool to give you all the information you need to theme your views.
The Views 1 conversion process is still a little (a lot) rough -- expect to have to do a lot of work to update Views 1 views to Views 2. Still, it does enough that the update isn't awful, and it's a good idea to really rethink the views anyway, since Views 2 operates so much differently.