Iphoto with ILife '11 vs Aperture vs other?

I'm an amateur photographer that is looking to improve my skill. I recently purchased a Nikon D3100 and am looking for a photo editing / organizing program. I have Iphoto which has been decent so far, but I think I've outgrown it!
What is the difference between Iphoto with the new ILife '11 and Mac's application Aperture?
Also, any opinions on Acdsee Pro 4? Compared to Light Room?
Again, I'm just an amateur, and I don't think I need the best of the best… The more user-friendly, the better!

I can't tell you what's best for you with that information. You need to visit the software websites and and see which features you need/want.