I've been trying to use TextMate to edit a few snippets of code (among which newspipe, where I'm trying to track down a couple of niggling issues), and I must say it feels wierd. It's not just the keybindings, its apparent lack of Python syntax highlighting or the general unMacness of some of its features (although I quite like the "filter through command", which is the one vim feature I've been wanting on an Aqua editor).
I've finally pinned it down to it having far too many menu options (and seldom-used features) for its own good. It tries to do too much, marring the Zen-like task of writing. The fact is, I've been using VoodooPad Lite for pretty much all my Wiki and blog posting, and I never needed anything more complex for standard notes.
And for coding, both SubEthaEdit (which has more than adequate syntax highlighting - especially for Python, even if it lacks folding) and vim (which does pretty much everything except being a Cocoa app) feel a lot more practical - I can instantly see what I changed in SubEthaEdit, and I can fold code and pipe text six ways from Sunday in vim, without lifting my fingers from the keyboard.
I'm not (and never have been) a BBEdit person. I like niceties like brace matching, autocompletion, macros, etc., but could never bring myself to rely on those. Back in my coding-for-a-living days, I found I was being spoiled rotten by Microsoft's Visual C++ and Brief (now that was an addictive editor) and swore off them when I took up vim. I'm not a vim expert (and never will be), but there's something to be said about needing to know as little as possible about an editor to get things done. - i.e., just doing it (with apologies to Nike), whatever machine you happen to be working on.
Which takes me back to my original point: Disregarding its bouts of unMacness, TextMate tries too hard to be a featureful editor, resulting in a lot of UI and interaction model "noise" that makes it hard to use. It also tries to lock you in by having lots of "nifty features" you can't live without, with the net result of increasing the learning curve (unless you designed it).
Still, it might spur development of other Cocoa editors. Maybe SubEthaEdit will get command piping and automatic brace closing. Until then, I'll stick to it and vim, and recommend you take a look at Smultron if you need syntax coloring for off-beat languages. It's free (always a nice "selling" point), feels quite a bit more Mac-like, and appears to be easier to customize (maybe even to do Markdown highlighting).