In reply to JDSwain:
I'm using a Macbook bro hooked up to my second Dell monitor and am pretty happy with my setup.
You don't have to go nuts on a second monitor. My Dell was around £200.
I used to edit on an iMac but didn't like the reflective screen. It's great for viewing images on, but I've had much better results editing on the dell which has a matt finish.
The guys in the thread are right. Editing programs need some good hardware to run them. Invest in a good laptop.
I use a colour calibration tool too, the Spydr 5 Express (an old one now) to calibrate my colour profiles once a month. I do this once for the laptop and second monitor.
Hope that helps .