See my experience is different. I have been building PCs for the longest time and almost nothing I've built has gone down due to faulty hardware. I believe generic PCs built by inexperienced builders may be unreliable but its not true to say that PCs are unreliable. It depends on the manufacturer. For example, at my current work we have about 20 macs and 120 PCs and at least in the past 3 years I've been there, I've seen more mac failures from power supplies, hard drives (in the G5 imacs...heat I guess), a logic board, ibook keyboard...etc. I've had between the 120 PCs, a HD that died, a PSU and a DVD burner. Its luck of the draw if equipment is well built.
You may have a good point about the viruses and spyware because inexperienced users may get more of those.
PS. I still have my first PC and its running as well
Its a 386-25Mhz with 4meg RAM. Its a retro dos gaming box at the moment. Its also from around '89
