I export the finished edit as MOV-file (in source DV compression) and use TMPGenc for encoding. My version does not produce MPEG-2 files for DVD.
One reason for the smooth operation is probably that it uses the. On my PC (P4 2.8Gh 1.5GB) this runs very smoothly. Somehow I just like editing with this stuff. In addition to using mouse, you kan work very efficiently with keyboard commands. The concepts like: Projects, bins, clips, sequences, settings, effects etc are defined just as I feel that they should be for large projects. The most pleasant experence is that Xpress is based on a very good and powerful conceptual model of video editing. After watching the videos, using Xpress for editing was quite straightforward. They are very good and quite instructive. I went through some of the instruction videos at Avids website.
It not a product you learn from scratch just by using it. This summer I edited a number of short videos in Avid Xpress Pro. Some years ago I was using Ulead Media Studio Pro for a large number of videos.