I've got a MacBook PRO that I bought about a year ago. It's got the dual core 2.6GHz i7 w/ 8 gigs of memory. Still a very respectable
computer today. It wasn't cheap, but it'll last me another 2 years at least. (This is my 5th MacBook PRO/PowerBook)
It runs Photoshop and Illustrator like a dream. It's not my main
computer, I've got a MacPro with 3 monitors that I use every day which has spoiled me.
The MacBook PRO isn't quite as fast as the MacPro with Photoshop but it's still screaming fast. (My MacPro has 32GB of Ram and a graphics card with 2GB of dedicated video memory and two quad core Xeon processors. Hard to match those specifications in a laptop)
The only thing I don't like about the MacBook PRO is it's a laptop. It's not as comfortable for me to work with it all day. I use it for when I have meetings or if I want to mess around with some files at the house. I'm also very spoiled with 3 monitors on my workstation. I feel lost with only one screen! I'm also a die hard Wacom tablet user so working at a desktop is the only real choice I have.
All personal preferences aside the MacBook PRO line of computers are very capable for graphics work. Add in a second monitor on your desk and a full size keyboard and mouse and you'd be set for a full on workstation.
The MacBook on the other hand... is great for office type applications but I wouldn't recommend it for any heavy lifting in Photoshop.