What I liked: well, I didn't actually like anything beside the ease of modifying/adding keybindings.
Some of what I didn't like:
* The whole UI felt wrong from alpha to omega and overly gimmicky: the whole thing relied too much on the mouse and the things that relied completely on the mouse like the options in the search panel were poorly sized/designed. The many roundrects and shades and gradients created a mess that left a very bad impression.
* The underlying engine is very poorly used by ST: just activating vintage mode is enough to tap a lot deeper than the default UI lets you. The engine is great but it only shines when you try to use it as another app. That's weird.
Using Vim is a spoiler, I guess.
I can't reasonably tell you to not make the switch. I have no idea what knowledge you have of Vim but I can say that I find Vim not only extremelly more powerful than ST but also a lot better designed on almost all fronts.
Once the beauty of subsitutions, :global, ranges, Ex commands, text-objects and motions is ingrained in your brain, using ST2 may feel like using (a pretty) TextEdit. Hell, even folding is nicer in Vim.
In the last year, I had the impression that a bunch of people blogged about their decision to switch to ST2 from Vim. Each time, I felt that the blogger didn't use much of Vim to begin with so switching may have made some kind of sense. If you are reasonnably advanced, I don't think there's any reason to switch.