I hear you: TextMate is a great editor, especially when you want to browse through a lot of code. That said, "e" on Windows is fairly TextMate compatible (at least it runs the TextMate plugins). For Ubuntu, GEdit and Emacs are very good. Emacs with Speedbar lets you whip through lots of code quickly. GEdit also provides good plugins and multiple directory code browsing.

All that said, I still boot OS X for specific apps (TexShop, OmniGraffle mostly). Anyway, it is a free world, and certainly OS X is a great choice for development.