1. Fast and responsive 2. If you write a plugin, you know TextMate is Unix (forked child process, communicate through shared fd, you invoke a command named dialog2 to let TextMate popup any dialogs or completion menu...). You can add editor commands in any language -- you can even make TextMate display complex UI dialog with bash. 3. File browser is nearly a finder (drag and drop like finder, and most finder shortcuts work) 4. Search (there are some hidden shortcuts, but when you master it you feel very fluent)
There are weakness too: TextMate is losing the market, many bundle developers switched to other editors. You can't find many new bundles nowadays. It still doesn't support vim-like keyboard operation... etc
Compared to Sublime: Better Find interface. I really hate the sublime multi-file search result list, it seems like a hack, not a real interface... I just don't get why they would do it like that.
I just timed it. Opening a new window on the PC I'm using right now takes between 70 and 72 frames, or between 1.16 and 1.25 seconds. On the rare occasion that I do it.
I understand that everyone is a leet uberhacker who is thrown off their flow by a butterfly farting on the breeze, but this is princess-and-the-pea stuff.
As for me, I've been using TextMate since it's first release more than a decade ago, and I'm simply used to it. I'm more productive in TextMate since I know where everything is without thinking about it.