I installed FuzzyFinder. However, the limitation is that it only finds files in the current dir. One workaround to that is to add FuzzyFinderTextmate. However, based on the docs and commentary, that doesn't work reliably. You need the right version of FuzzyFinder and you need your copy of Vim to be compiled with Ruby support.
A different workaround I'm trying out now is to open all the files I'm likely to need at the beginning of the editing session. E.g., open all the files in key directories...
:args app/**
:args config/**
:args test/**
etc...
(This means I would have possibly scores of files open, however so far it still seems to work OK.)
After that, I can use FuzzyFinder in buffer mode and it will act somewhat like TextMate's command-o
shortcut...
:FuzzyFinderBuffer