While TextMate is nice, and I paid for it myself, I recently decided to start learning Vim because you can essentially use it on any platform. It may take some time to learn, but I believe it will be greatly beneficial in the long run.

I urge you to check out MacVim (http://code.google.com/p/macvim/).

You can add many of TextMate's features to Vim using plugins like snippetsEmu.