I have owned each of the different (Aluminum) models, and i can safely say that they were all solid, excellent purchases. The most recent one was the 17" Powerbook that came out earlier this year and I never had any issues with it. Design, reliability of the OS, longer battery life, very bright screen, runs quieter than equivalent PC notebooks, lighter and thinner, you can't go wrong IMO unless you are a gamer (there are not nearly as many available for OSX) or an online poker multitabler...

If you are planning to use it for, say, four tabling Party Poker and cherry picking games from other sites while datamining with Pokertracker and using a HUD while playing, then not only will you have to use Virtual PC and take a drop in performance, but you will also have to deal with overlap if not using an external monitor. Then again, the latest release of 17" Powerbooks would support two tabling no overlap pretty well.