Can I just mention here that Liquid Edition 6 onwards will edit MPEG2 natively through using a patented method which I think has something to do with Long GOP. I think I once posted here somewhere how it could get round the traditional I-frame versus B-Frame editing issues. I can't remember now how it does it other than there is some way it actually creates the full frame when editing before (I think) converting it back.
The result is that to my knowledge LE is the only editing package which allows full native MPEG2 editing and with no interframe restriction issues. Although I stand to be corrected on that last point.
Um..just thought I'd mention it