In my case, the iLife suite was better than what I had or could find on Windows, ditto with Final Cut Express. On Windows I used Pinnacle to capture video, but ended up using the trial version of Sony Vegas to perform some video tasks. Pinnacle simply crashed far too often, typically with larger video files, but it imported video like a champ. Vegas, on the other hand, allowed me to edit perfectly, and never crashed. The problem is that it would not see my video camera.
On Windows I also edited pictures, put them in a photo album, created books and slideshows to DVD -- but it required several programs to accomplish it all. It was clunky and time consuming. That has been replaced with iPhoto for the editing, slideshow creation, and book creation. One export to iDVD and the slideshow gets burned to DVD. I know it's not professional quality software, but I just do this for family and friends. Sometimes I import to DXO Optics Pro, so that adds another step, but that's only if I want to fix camera/lens aberrations first.
TechieXP, if I'm not mistaken, also uses his Mac for video editing, even though he's very much pro-Windows. For the low to middle end video editing, Final Cut and the Express version are very good. If you're into pro-level editing, then Avid is the way to go, but I'm just a rank amateur -- I know it and freely admit it.
I liked Vegas a lot, but it just would never see my camera. I even did a re-image without Pinnacle installed and it didn't help. There might be other software out there that works well, but like I said, I value my time much more than money, so it was an easy decision to get a Mac primarily for the software that I mentioned. Oh, I knew about that stuff because I had a Windows PC that I decided to try and get OS X running on -- hackintosh it.