Most people don't understand that Quicktime is more than a player. For us Mac users, it's some kind of graphic OLE. And, to the guy who has problems with the responsiveness: Sure, only because it is unresponsive on YOUR system, it's shit. I mean, it works flawlessly on my Quicksilver, as it does on my Cube, as it does on my MP 450 G4 at work, on the Powerbook G4 of my boss, on the Powerbook G3 of a friend of mine, on the iMac at work....I NEVER heard such problem. Quicktime is rock solid, and I never - on no system - had problems with it! I can move windows at a lightning speed (do THAT under Windows!) without a dropped frame or sounds problem, even when playing DivX.
Quicktime is simply one of the best standards I have ever seen, sadly, only on the Mac (since the PC Quicktime is somewhat equal to the Mac Windows Media Player...both are not that good).
About the MPEG 2 thing: You can only play them in DVD Studio Pro, and even there, not in fullscreen. But, of course, you could decode them with Quicktime if you have the MPEG 2 codec, which comes with DVDSP. I have no clue where else it could be found (*cough hotline *cough). I also hope that soon there will be a MPEG 2 player. DVDSP shows that it is possible in great quality, no dropped frames, no dropped sound, just incredible. I remember that there was a hack for the classic DVD player which made it similar to the version which comes with DVDSP so you can open Video TS folders on your harddrive. IIRC you can even do this with the standard OS X DVD player. Now you "only" need software which packs the MPEG 2 stream and the audio stream into a VOB file inside the Video TS folder with the needed info files...which would again be DVDSP...
remember that a simple MPEG 2 player wouldn't help, since MPEG 2 can't save the audio stream inside the MPEG 2 file. BUT of course,an MPEG 2 player would let us play SVCDs. Rumour are that the next version of toast can burn SVCDs (praypraypray), so they will include a MPEG 2 encoder, and hopefully, also a decoder along with a small SVCD player which would solve this problem.
Until then, of course, there is VPC and the SVCD / MPEG 2 players for Windows/Linux, but well, that's another story.
Oh, and Natchoheat, I send you PM, hope you got it