Does anyone have good suggestions for the h.264/.mts files you get from a Sony HD handycam when shooting in HD?

Nero manages them, but holy cow, is it slow. And there doesn't seem to be a good HD output option; I can finish in good quality MPEG-2 or MPEG-4, but it's not HD.

What I'd like to do is edit in HD, save in HD, then downsample/convert to MPEG-2 for DVD's or Tivo.

Thanks!

Steve