I got a Mac not long ago with iLife '06 on it. After using both Windows Movie Maker, then moving on to Sony Vegas Movie Studio Platinum 7 before ever buying the Mac I'm not impressed by either iMovie or iDVD overall. iDVD might be ok if they took off the Apple logo on the bottom right corner of the menus and then made it compatible with my video files and then I could make an ISO image to burn to DVD on my PC (don't got a DVD burner on the Mac). You can make an image of it, but it's in .img format, apparently Windows isn't supporting it... It's got some pretty cool menus and stuff, but it would be a big pain to transfer all the video file to the Mac to make the DVD. As for iMovie, maybe better than Movie Maker in some ways, but I still am not a fan since I got something more advanced. It would be just so much easier to get a video editor that works with Windows... Vegas Movie Studio is cheap enough, more advanced than iMovie, and easy to use, it also comes with a DVD authoring program (DVD Architect).
I do like Garageband on iLife a lot. I am not very good at making music with it, but I still think it's fun to do it anyway.