I tend to use QT Pro for posting fast clips with minimal bells and whistles on my site and my work site (eg, see
http://www.bikefriday.com/route66) - I use a simply digi camera in movie mode. But I am about to use iMovie to make a 45 minute DVD movie with almost 300 minutes of footage shot on that trip. iMovie lets you do nice things like fades, fancy scrolling titles, Ken Burns effect (moving stills etc) that you can see in e.g. the 1 and 3 minute trailers of a movie I did last year:
http://www.galfromdownunder.com/peru
BUT the @#$% about iMovie is that it blows everything out to '.DV' format (I'm told). Which means a simple concatenated movie in QT might be say, 200 Mb, it blows out to 10 GB or so in imovie by the time you add your bells and whistles, then winds up as an additional 2Gb (say) DVD movie via iDVD. And to make the disk image, from which you burn the DVD, takes hours.
Make sure you have a ton of freespace to process your stuff using iMovie, iDVD ... the s/w tends to get in a bind when you don't. As in, take 4 hours to make a disk image and then crash etc. Not fun.
When using QT make sure you never delete your originals. I still screw up and get 'Can't find file' because I pasted together a whole load of clips, saved them as a reference movie, then somehow trashed one of the components. Will I never learn.
Powerbook G4 12 1gHz 60 gb Mac OS X (10.4.2) Using two 11gb Seagate pocket drives on the road to store and process movies. hope it works.