naw, you can do pretty much everything in AVID Express -- DV Express is DV-only, but the "full" Express can edit and output a lot of formats.
basically Express is AVID's bastard son that was put out to try to compete with Final Cut - and presently it isn't doing so hot at all. Final Cut is just such a good mid-end suite, and Express is just trying to catch up to it. I have limited experience with Express, but I do know that not a single place i have worked, nor person i know in the industry uses it. all mid-end stuff is FCP exclusively.