I can't believe someone would flame a brand in here. Ignore that garbage. I have had a Mac notebook (powerbook) for more than four years and it's been outstanding. Still running strong. I also have a larger Windows notebook. Those Macs are physically very durable and well built. The OS is a personal choice and preference that you have to decide. I use both Windows and Mac OS together with no problems. These days they play very well together. I find old Macs tend to remain useable longer than old PCs before you outgrow them for some reason.
The iBook has a 30GB HD and a dedicated 32MB ATi9200 chip but an internal wireless card costs extra. The IBM has built in wireless (as all notebooks should these days), but has a smaller 20GB drive and crappy integrated graphics with shared VRAM. Both have slower but adequate 1GHz CPUs that will perform similar tasks at similar speeds. By comparison the IBM should be a little cheaper than the Mac but it's not, it's $500 more. This 12" iBook is a great value. A co-worker bought one and it's very sleek. It will cost you about $79 more to add the internal wireless-G card.
Often the online resellers such as MacMall, or CubMac will give you a better deal while still honoring educational discounts. Typically they toss in free Ram upgrades, free wireless, or free case, etc.