I got really used to TextMate's Esc behavior also. It's amazing how often you need a word that's close by in the same document, and the first letter plus a few taps of Esc worked great.
My adapted behavior is to just be a bit more verbose to get ST2's tab complete to find what I want (e.g. to match ActiveNav I do something like Ana[tab]) -- but I often end up with the common complaint of an obscure PHP function (e.g. an[tab] gave me apache_note(note_name) .. err).