I bought Aperture, but don't use it due to the fact that it doesn't support my Fuji S2 or my Nikon D200.
Maybe there is a work-around for the S2, but right now I'm playing with the Adobe Lightroom beta and I personally think its pretty cool.
Aperture does work with Nikon D200 as I use that all the time with no problems, it's the D300 that having problems direct from camera, but I overcome by using the card via sandisk card reader