I've never even encountered this type of keystroke-level undo until TextMate, and I find it slows me down considerably. Please make chunks a preference!
It will appear in 1.3 (no exact ETA).
I'm disappointed its two full point releases away, but thanks for being this specific, most devs wouldn't be. In the meanwhile, is there any means of mimicking chunk undo behavior? Perhaps an "undo from history"?
Re: slowdown, I read about something involving the caching, and I did flip a defaults write, so app switching does seem a bit better..but tab-to-tab is really sluggish, and I'm on a dual 2 G5. This is just a text editor, I can't imaging what's happing behind the scenes that causes this.
In b17 tab switching got a lot slower because the scope parser is done using an ANTLR generated parser, and it's used a lot (at least when switching tab, because it needs to match apply styling using the rules set in Fonts & Colors) -- most likely I'll introduce caching for this in b18.