I have home made computers, dell laptop, Asus laptops, etc. I use ubuntu as well (netbook).
With windows 7 I need no other OS. The same isn't true for MAC, which is probably why they sell windows 7 on their website.
Computers can have problems, MACs are no different, quite a few of my friends have macs and most of them have no problems, some have had problems, hard drive failures etc. But a hardware failure is no reason to change OSes, it is a reason to go with a better vendor with better hardware or to replace existing hardware with new (even in laptops).
I saw the comment that MAC is a better development platform. Having experience in programming I must say windows Visual Basic is one of the easiest and most powerful languages out there, as long as your environment is windows (generally it will be). Adobe makes software for development that beats MAC software (final cut etc) and is useable on windows.
I'd just like to point out many of the reasons posted by mac users for using macs are mostly invalid (I dont have viruses, I dont have hardware problems on my Dell laptop either, Macs are actually proven to be easier to hack into as shown at a fairly recent week long event, Vista took 3 days, mac took 12 hours, ubuntu wasn't hacked into for the whole week). If you like cute computers, and you are not computer savvy, right now mac will help you with that issue. If you want one OS to do everything , Windows is still the most versatile OS on the market and the only OS needed.
Hope this helps.