I program primarily in Ruby and C#. I'd like a code editor that can gracefully deal with incomplete code; by that I mean a code editor that doesn't protect itself from syntax errors by auto-adding matching braces and quotes, but one that pays attention to the tokens you add, and identifies that an unmatched quote doesn't mean it should syntax highlight the next 5 pages of code as a string... it should instead put some kind of squiggle or mark reminding you to close the string (or code block, or whatever).
Are there any editors out there that properly identify new tokens as the likely source of syntax errors, rather than treating the entire file like a batch process and warning you that all of a sudden you're missing a closing brace 300 lines down at the end of your file?
As far as OS, I use Linux and Windows about equally, but I prefer my IDE to be in Windows; if you can point out some awesome X based editor (no, I'm not fond of vi or emacs style editors, sorry) I'd be willing to take a look.