I've had a problem with TextMate (and with OmniOutliner), where writing in very long lines was extremely slow. Very slow.
I've just updated the utility FruitMenu, since the update claimed to fix a problem where writing in OmniOutliner was very slow. Guess what, writing speeds in both applications have dramatically improved.
It might be a coincidence, but then maybe not.
/Peder Axensten