Hey,
just wanted to let people know I've released AckMate - a plugin for searching your project files with 'ack'.
It offers significant improvements over my previous ack-in-project bundle, such as per-project windows and settings, filetype selection, and a much less annoying UI.
It's currently only compatible with OS X 10.5 and above (and only heavily tested on 10.6).
Source and binaries are included in the github project at http://github.com/protocool/AckMate and the project wiki contains instructions on how to use it.
Regards, Trev