Thanks for those suggestions.
Vico looks like the exact thing I'm looking for, but I read in the dev's blog that he plans to eventually charge $50 for it when it's out of beta, which imo is a lot.
I tried MacVim, but it crashes every time I try to open a document. I got the latest Github version, but it's probably incompatible with Lion or something (or I'm just screwing up).
I'll stick to TextWrangler for now, it's a little more advanced than what I need but it's free and loads fairly quickly. I'm considering buying Smultron, it costs €5 on the App Store and it looks really neat.