Moved over to Mac with the MacBook pro in the summer after being a dyed in the wool windows user since version 2.0. I must say I would not go back. The changeover proved to be a remarkably painless experience. The Mac is so much faster, slicker and easier to use. The hardware and engineering are second to none, with a real quality feel. The experience of using OS X is far superior to Vista although I must confess I haven't installed Windows 7. Probably the most noticeable thing is that the Mac just works without the fuss. Standard software is excellent with itunes, and iphoto being very popular with everyone. iphoto is especially impressive for viewing, sorting and editing the family photos. I have also added MS Office, because I use it at work and wanted the compatibility. I would also recommend VMware Fusion just in case you want to run windows. So simple to use. Just connect your old PC to your wireless network and run the Fusion PC agent. Connect up the Mac to the network, fire up Fusion and the software will detect the pc & create a virtual copy on the mac for you. Disconnect the PC and flog it on ebay. Whenever you want to use a programme or read data that was on the old pc, just fire up Fusion and it is as though you are sat at the old pc. I still use it for garmin mapsource and my sat nav. Connects perfectly via usb.
The MacBook proved so popular with the rest of the family that I was always at the back of the queue and couldn't get my hands on it. In the end I bought the imac 21.5 for the family just before christmas. 27 inch is fantastic, but just too expensive for me. The higher end Radeon 4850 is really a must to drive that many pixels. In the end I went for the 21.5" with Radeon 4670. Performance is superb and I have had no problems at all. If you are still at college, or if you have kids/ relatives still at school, don't forget to use the Apple education store.
http://store.apple.com/uk-edu No point in paying full price.
I would also recommend time capsule for backup and online storage. So simple to use and can be read by PC and Mac alike.
Can't really help you much over the x-box as I don't have one. Generally Macs are not renown for gaming, although I have managed to convert Oblivion for the kids using cider rather than running via bootcamp. If you are new to OS X then the Apple site has some useful guides for windows users which are useful.
http://www.apple.com/findouthow/mac/#switcher 