I'm a huge Mac fan (no, not overweight!) and I must say that you must be having some poor experience of Macs. I think first of all I'd like to note that your Mac experience is centred around your school machines, now this is fair enough, except that these machines likely see a lot of different users all doing different things with varying degrees of care.
A similar example; I do part-time work in a hospital, they have Dell machines there, only one or two people use these machines each day, and only for a limited number of taks. They're getting a little dated now but they work fine and have only had minor hardware failures over their lifetime.
Meanwhile, at my old high-school they had Dell machines (the same ones) and at any time any class-room would have at least 3 (of 20) machines with faults, wether it be not starting up, a buggered mouse or colour missing on the monitor. Roughly six or seven machines would be replaced each month.
The point I'm making here is that any OS if used with some measure of care will run just fine without crashing. The real up for the Mac OS is that it is much harder to make a mess of than Windows, SP2 sounds like it might be a significant development in this area, but the entire core operation of Mac OS X makes it difficult to mess up key elements.
In regards to hardware, Macs are actually very competitive, now the clockspeeds are obviously different, but clockspeed has always been a pretty poor measure of performance. Performance is actually extremely good and in fact greatly exceeds many chips in some areas. Take a look at the Dual 2.5ghz Powermacs, they beat most desktops into the ground, both in performance and the sheer weight of cash you need to get one (I'm trying =). On Photoshop tests the Dual 2.5ghz beats a pentium 4 3.4ghz machine by 108% (that's less than half the time taken to do the same thing, on a machine that is theoretically only about 50% faster).
Lastly, it is possible to overclock a Mac processor, I'm not sure where you heard that you couldn't, in some cases it is a bit more complicated to do it but it is entirely possible.
For my personal Mac experience, I am currently using a 400mhz g3 (CRT) iMac which is some 4 or 5 years old, it is running OS 10.3.5 (the latest version of OS X) and it has an uptime of some 97 days excluding restarts for system updates. It runs quite smoothly, even though its slowness due to age does show through. The only hardware problem I have had was with the power-supply (it didn't like being next to a radiator and died).