I have one Uber i7 quad core 15 high spec" + a 27inch Monitor.
and an iPad 2 along the way.
This is ideal for me because the new MBP's are as powerful if not more powerful than an iMac so it does well as a desktop replacement. And when I need to do some kick ass work on the fly I've got a monster in the bag with everything that I need. and if I don't i'll just bring my iPad, which is lighter than my macbook air which i plan to sell once my ipad 2 finds me.
my old set up was PC gaming rig, macbook air, iphone