Just to mention a few things ...
Just on those two, I think most HTML editors use the shortcuts mentioned above and probably the most painful thing when you migrate is trying to get used to a whole new group of shortcuts. I think the ⌃> works better in some ways for closing tags as you don't have to tab back in to add an ID or class to a DIV you just closed.
I just wanted to be clear (maybe the initial reply was buried by the avalanche of replies to the code sense :-) but it's not ⌃> that does what you'd like the "closing bracket type-hit" to do, but rather ⌘⌥. (<- that period is part of the keystroke, not the end of the sentence). (<- this period is the end of the sentence)
The two are quite a bit different, and both very handy.
The ⌘] or ⌥⇥ shortcut is a pain for indenting though and I still hit TAB everytime and delete my text. These are only small things, but when using on a day to day basis can be annoying.
One thing to keep in mind here is that the ⌘] key combo has been the defacto Mac OS key combination to indent highlighted text since way back when Steve Jobs was wearing diapers. So it's not TextMate that has to change, but rather the other OS X apps that brought their windows shortcuts along with them ;-)
-steve