I honestly tried to drop emacs in favor of TextMate for hacking scheme. It has the buzz, a great philosophy with a really stand up developer hacking it, sexy integration with osx, subversion hooks, nice bundle system, file browser, intuitive shortcut keys, seemingly deep regex support, and on and on.

The issues I ran into with TM for scheme were really fundamental. While TM has both scheme and lisp bundles, they don't seem to handle code indentation nearly as well as emacs. Proper scheme indentation was mostly a manual process.

The REPL integration is also much better in emacs, in my opinion. That proves to be a huge time saver. REPL integration in TM amounted to opening up terminal.app in a separate process.

These two things - code indentation and repl support - were two things I couldn't look past. They are the bread and butter of scheme hacking. I would love to see TM improve in these areas.

If you're lisp hacking I think you'll be best served by slime/emacs. That combination is the best environment I've found.