There are quite a few things that textmate does not have but should have to be a full featured text editor. off the top of my head the main ones are: split screen, better printing control, better plugin system, ability for a real lexer/parser/tokenizer to be plugged into the plugin system(I guess you could get around this by writing your scripts in ruby and shelling out but that seems slow.) Regex for syntax highlighting your files breaks very easily. I might be way off base and all these are easily fixed with some plugin but I haven't found the solution to them yet.