Good thread. I've been wary of iPhoto as well. I'm not going to argue that the fear is rational, but after a couple of dry runs in 1 and 2, I haven't felt like taking the time to learn 3, so I just import photos into subfolders in the Pictures folder. It's rare that I can't locate an image quickly this way, and I can always use the Photoshop browser (I'm often working in PS anyway).
As I recall, when I first tried iPhoto, rotating images was lossy. I believe they've fixed this, but it still made me wary. Then I recall some problem with using Photoshop - iPhoto saved the unedited original for you, which was nice, but the original was hidden, and you couldn't save layers or something, or multiple edits. Is this still true? I'm sure there were workarounds but it was easier to just use my own folders.
Then there were the usual speed problems, etc., although it sounds like this has largely been overcome. It's comforting to know that you can just drag an image to the desktop to make a copy. Maybe I'll give it another try.
For some reason one feels a greater loss of control with iPhoto than iTunes, perhaps because some of us are more likely to want to edit images than music files.