Dbld: I was agonizing over this choice a few months back, and like you, I use a LOT of Photoshop (and Lightroom), serious amateur in photography, etc.
I decided to go with a Mac Pro (and as a few others stated, a new version with updates is expected in just over a week, so I'm waiting as well), rather than an iMac. Here are a few reasons:
1. This will be a very long term use computer for me. I'm buying Pro (and a decent amount of RAM, probably 6-8 gigs) because I want this system to last me 5-10 years. quad/octo core xeons are crazy fast compared to core2duo, so Photoshop will fly, and you should be able to do a lot of video editing as well.
2. Having a separate monitor - To me, one of the biggest reasons I didn't want an iMac is the glossy screen. Photos *do* look beautiful on it, but the potential glare and the extra color saturation aren't good for color correction and making sure my prints match the screen.
I recently upgraded to a Samsung 24" widescreen monitor (
245BW)
and it gives me a ton of screen real estate for all of my Photoshop palettes as well as multiple images.
3. Expandable RAM/Hard Disk space - The Mac Pro can handle up to around 32 gigs of RAM, so if you start doing serious video work that requires RAM, you can always add more.
There are also 4 drive bays for internal SATA drives: you just screw the drive onto the carrier (screws built in), then slide the carrier back in. Couldn't be easier. I think the max now is 4 terrabytes - again, very good for disk space-sucking images and video.
A nice side effect of getting such a powerful system will just be how incredibly responsive it will be for all the mundane tasks you do every day, where you might actually notice a slowdown in windows, depending on what you're doing.
So those are my reasons for going Pro over an iMac. Just remember, buy the BEST you can afford now - and it should last you a LOT longer!
Good books on learning Mac OS X:
David Pogue -
The Missing Manual - Leopard Edition
David Pogue -
Switching to a Mac - Leopard Edition (probably available late January/early February)
Hope this helps, and enjoy your new system!
-Bryan