The most succinct result I can give is: horsepower helps. It’s amazingly simple to do stuff like titles, music tracks, transitions, but boy, is it CPU-intensive. I am doing all this on a 500 MHz iMac DV, and I have run into multi-hour render and export jobs. Rendering titles is very well-done: the renderer takes a long time but it doesn’t bog down the machine at all. Exporting is just brutal. I am pulling a load of 6-8, with no other processes running.
The only feature I can think of to add is an estimate of disk space as well as of time to complete. If you’re trying to scale something to fit on a CD, it would help.
For example, I have a 19 minute project that takes about 140 minutes to export as a quicktime movie: it would help to know how big it will be so I can see if I’m wasting my time or not. If it’s too big for a single CD, I’ll need to work on it some more.
Update: The movie came in at 460 Mb or so, so it was fine for a CD.
The camera worked fine, though I think it came with a flaky firewire cable: I swapped one of my own in and it seemed to work better. The symptom was dropouts and extra clips: I had to extract the video a couple of times and would get different numbers of clips.
Firewire itself is very nice: I love a standard that more than one company supports. You drive the camera from the computer as soon as it’s detected, so you never need to touch it after that.

You should look at Adobe Premier - I’ve found it to be much faster.
Yeah, but with iMovie the price is right. For home use, it’s fine. The guy at the rental shop suggested Final Cut Pro as the tool of choice.