TextMate 1 has the lovely ability to save any modified documents when the editor loses focus (say, when you command-tab to iTerm to see your test results.) This suits me well, as I rarely, if ever, don't want all edits to be persisted.
TextMate 2 has seemingly lost this ability out of the box. But there is hope! Simply install this lovely little bundle (using a recent TM2 build):
Presto! No more explicit Command-S for me!