I searched around a lot for the same ? ktwse,
I'd definitely trust fdog (James) advice about Photo Mechanic. He is a pro and knows!
Also loftus seems to have a fair bit of experience with Aperture and I read a lot about it - the interface is really cool but Aperture takes a lot of system resources, i.e., latest mac hardware, lots of memory, etc. to run well. Still it is probably the "coolest" WTG. B)
I don't think you could go wrong with either of their suggestions - just stick with it and learn the pluses and minuses of the programs.
BUT after much deliberation I recently went with Adobe Lightroom. There are features I really like and am used to that the Lightroom interface has (like chromatic aberration correction) and if you quickly join NAPP (National Assoc of Photoshop Professionals) before Friday, you can get a code and use it before the end of Friday to get Lightroom 1.1 at $199.00 (instead of $299.00). Now it costs $99 to join NAPP but you get lots of perks and discounts. Better than just paying $299 for Lightroom.
I also suspect that Lightroom will allow 3rd party plugins like Noise Ninja, etc in the Lightroom interface in future updates. This would be great as noise reduction is best done at the beginning of RAW processing and the usual supplied RAW noise processors are very lame. Anyway I suspect the "plug-in" future of Lightroom might be an actual asset.
I'm a "mac" person and it was hard for me not to go with Aperture, but I think I'll be happy w/my decision for the future.
But of course fdog (James) will always run rings around me with his Photo Mechanic - but then I'll never be just like him will I? 
Best, Carol
PS oh I didn't answer your ? on iPhoto. I've used it (but not the new iLife '08 version) and it is fine for hobbyists but awful for lots of large raw files etc. I always get strange color shifts when I use iPhoto even when I told the program to use my embedded color profiles and just "point to" the files, not import them. Very strange.