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vim. I rarely use the gui version of it, however when I do, I use macvim rather than gvim.
 
Funny the OP should mention TextEdit. Snow Leopard has totally revamped TextEdit with more options and functionality. This is just one of the things I like about SL, people think Apple didn't do anything to it but under the hood stuff but it's always the little things that are purposely overlooked since people seem to care only about what they see immediately upon boot.

So if the OP decides to upgrade to SL soon he might want to drop by an Apple store or Best Buy and check out TextEdit on SL and see if the upgrade offers some features that will satisfy him.

I have to say, I am pretty impressed with Snow Leopard's version of TextEdit. For basic text files, you can't really go wrong with it.
 
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