I don't know how it goes with PCs, but I get 4-5 years of use out of each new Mac before memory limits start getting too serious and things start going wrong. Bought this one last year and it was only my sixth machine in 24 years.
I've had my laptop a year last xmas, it's already had to go back for a new HD, and I've just recently spent a bit of money on replacing the power port, though that was partly my fault for tripping over the wire. Also the battery f***ed pretty much straight away, where as the one's in the new Macbooks claim to last for 5 years before being reduced to 80% of it's capacity. My friend got a Windows computer at the time as me and his is now running slow etc despite having anit-virus softwhere, experts looking at it etc. Windows is constantly pissing me off now, and the computers just don't seem to be built aswell as Mac's going by reviews on Mac's. A windows machine usually would last me 2-3 years, though I doubt my current laptop has got that much life within it.
I had to replace the hard disk in my last MacBook after about 18 months, and the Airport card after about three-and-a-half years, but those are the only times I've ever had that kind of disabling hardware problem except for when I burnt out the power supply on a three-year-old Mac Plus after working on it frantically to produce a publication in 72 hours non-stop.
The 2004 MacBook was probably the least reliable, in hardware terms, of all the Macs I've owned -- there was a battery recall, and I had to replace the power lead after four years because the plug had got a bit bent after I'd finally tripped over the cable one time too many. (The magnetic thing on the new one dispenses with that prob, as someone just pointed out.) The titanium case was a bit buckled and dented by the end, too. One the other hand, it had travelled a real lot without any problems on the road, and had even been to the Sahara desert twice.
The new one feels loads better. The all-one-piece casing is much sturdier, the keyboard is both easier to type on and lets less dust into the inner workings (don't have to clean it so often), the trackpad is miles better, the speakers are good enough that I now often don't bother to take a remote pair with me when I'm travelling, and it's fast as f***. I preferred the matt screen and the front positioning of the disc slot on the old one (on this one it's on the side at the back, and I find myself always having to move things out of the way when I need to insert a CD or DVD) but they're quibbles, really.
