It's been a long time since I bought a new computer, the days of upgrading every few years have seem to become less of a necessity. I am very happy with my new purchase thus far....
Features which I am using and plan to take full advantage of--
-Intel Mac's, means windows can run great! I'm currently using a trial of Parrallels (VMWares competitor) to run windows applications alongside my Mac ones. This is very important for ASP.NET development, IIS testing, and simulating an environment which I support and work in.
-Bluetooth audio support - I've beamed music across the room to my Sony MBR-100 and my brothers Jabra bt3030, it's been working great.
-SD Memory card slot - great for picture syncing
-Calendar and Contact sync with my online accounts - MobileMe syncronization is a snap, I'd mention how to do it, but its so easy instructions aren't even needed.
(Separately, I'm syncing my iphone with the same Email/Contacts/Calendars, and together they are quite powerful)
-Iphone development and simulation with X-Code - I probably won't be able to experiment with this, or jailbreaking the latest iOS and updating my iPhones firmware until around the new year. I'll let you know how it works out.