Stop misinforming people!
I had a PowerBook G4, which I played Wow on, it ran oki in elwynn forest, but when we started SSC raiding it got hopeless, 4-6 FPS.. (sold it in 2007..)
My iMac G5 hardly manage to load Dalaran, it takes two minutes to get from the inn to the bank..
I replaced it (PBG4) with a 2007 MBP, which could keep 30-60 FPS in SSC, with almost everything maxed. In WOTLK, it would dip below 20 FPS in Dalaran from time to time, with most settings on medium. In 25 man ICC raids it would dip below 15 FPS on Marrowgar (settings still medium), but everything else ran at 20-40 FPS inside ICC, and questing in the 30-60 FPS range.
The 2007 MBP (with 8600m) is almost identical to the 13" MBP in terms of gaming performance.
I now have the i5 15 inch, and it runs everything maxed, except AA and shadows. I'm getting 40-80 FPS in raids, with occasional drops to 20-30 on Marrowgar and in Dalaran. When whelps spawn in ony25, my fps goes down BELOW 10 FPS for a few seconds as well.
To max WoW, you need something else than a MacBook Pro, because you cannot max it on the 15 inch, unless you want FPS drops below 15-20 FPS from time to time.
The 13-inch MBP will run WoW great, if you can turn down a few things, but maxed no..
edit:
stolen from barefeats.com
26.6 FPS on ultra setting in Thunderbluff...
The 15 inch gets 57 FPS, which makes conclude you would get half the performance in raids..