Eclipse - GrrFor the first half of our compiler design course in college, we're using a Java based lexer/parser generator called Coco/R (there are versions for various other languages), I think because it produces recursive descent parsers. Now, it's quite nice, really, but it has horrific syntax, so an editor mode is called for. There doesn't seem to be an Emacs one, so I had to resort to Eclipse.
Eclipse is odd. Since I last used it (a year or so ago) the interface has become considerably more cluttered and weirder. I think if I was coming to it new it'd take me quite a long time to learn it, whereas when I started using it four years ago it was quite intuitive. Also, the first time you do anything, it's bloody slow. Once you've done it once, it gets faster; I suspect this is something to do with Just In Time compilation. That's not really the point, though; the first time gives you a general impression that Eclipse is slow, and that impression doesn't go away easily afterwards. No way to avoid this, I suppose, but it's a shame.