I am using a Mac that came with IPhoto but my other computer was a Dell and I had Picasa on that one. I like Picasa better but is that available for a Mac?
Have you messed with iphoto much? At first I really disliked it, but after learning more about it I like it a lot, and you can't beat the price. Go to apple and watch some video tutorials is you haven't already.
I'm going through the same thing with Aperture. I got my hands on a free copy but It sort of sucks but it seems stupid to shell out the loot for Lightroom.
I found Picassa was working nicely on my Dell. I' am printing on a Epson Stylus R 380 and my photos would turn out exactly the same as they appear on my Dell screen (laptop). However I had some problems with my Dell connecting to the internet. I bought a Mac which works like a charm, but it came with iPhoto. When I print my photos they don't show up the same as on the screen. I usually have to make them look "lighter" on the screen in order to end up with a good print. Out of the 20 different photos I print I have to throw on the average 3 in the garbage and need to adjust "on screen" (make lighter) in order to get a nice print. I calibrated the screen properly but I keep blaming it in iPhoto. I am waiting for Picassa to come out with a version that works on the Mac. (Or get rid of the Mac, but it's getting expensive buying other computers, fcol!)
I'm no pro at this but I had a similar problem with Vista, I would try changing your ICC Profile that your Mac uses. Here's a link http://www.adobe.com/support/downloads/detail.jsp?ftpID=2956
