Just made one test video with Kdenlive (thats third from me) and for MPEG-2 quality is just fine but with loseless video (codec ffodivx) it's more awesome then fine :)
and this software for sure is the best video editor on Linux, with most usefull effects and futures !
http://www.youtube.com/watch?v=vNGRooshapI

here is first:
http://www.youtube.com/watch?v=19J1ImotEt4
and second:
http://www.youtube.com/watch?v=PNoHuffgzHQ
of course they was simple just to try start use this program and understand how usefull it could be.