... It seems everyone swears by Aperture. Why? I like to keep it simple, why spend 200 bucks? I already have the Cadillac; I'm I missing something?
No, you aren't missing anything. I always recommend people use iPhoto until they have a good reason to switch. For most, iPhoto is just right.
Why switch?
1) You have 100,000 photos in your library and you typically do shoots with 250 images and you ar finding that iPhot is to slow. Aperture is quite a bit faster when you have many files
2) You have a notebook and desktop and need to move
parts of your library between the two
3) you like the extra image adjustment controls Aperture has or you need to work with IPTC metadata
4) Aperture allows for more complex folder/project/album configurations. It's pretty much unlimited that way.
5) "Vaults" are nice. If you like to keep multiple backups and have an easy way to sync them while you work. Many other backups systems require you to wait