If you're planning on doing any kind of gaming I would recommend getting a MacBook Pro. The base models are not that great for gaming and are really very expensive for the parts list you're getting. (Although that's not everything for a laptop or any Mac for that matter.) Now that Microsoft has released their Office 2008 suite for Mac it is fully compatible with the ".[doc/xls/ppt]x" files from Windows Office 2007 so there are no problems with having to save everything as an Office 2003 format to transfer to a Mac.
Be careful to specify a graphics card, my mum bought a MacBook Pro from a store for video editing, only to install final cut pro and have it tell her you can't run the program with onboard graphics.