Chime team member here.

That's one reason exactly. TextMate is a phenomenal piece of software, and I've used it for years. Will continue to use it probably. In many ways, it was an inspiration for Chime. It can do many things Chime cannot. But, TextMate does not offer the same language-level support, syntax highlighting accuracy and speed. And, I like to think Chime has a more refined UI, but that's a personal thing :)