My Mac experience has been excellent over the years. So far I have owned a Performa 5300, PowerMac G3, and a 24" iMac.
The breakdown:
1. Performa 5300 is going on 12 years old. During that time, the only repair needed was when it was brand new. The monitor that shipped with it from Apple was damaged and lost it's red output. Once that was fixed, no issues at all with hardware of any kind. System 7.5 had some moments of unreliability, but once I moved to system 8, the machine has been virtually bulletproof. My Dad still uses this machine daily for all his invoice and billing needs for his business.
2. PowerMac G3 266 beige. A very fast computer in it's day, and very capable. This was my learning machine and experienced a ton of dabbling hardware wise. I swapped out hard drives, added internal SCSI CD-RW, maxed the RAM, created a slave HD setup, and added an internal ATI card. The only failure this machine experienced was a bad IDE cable (my fault) that would sometimes cause the drive not to be recognized on boot. This machine still runs great, but was replaced because the cost of upgrading it any further was greater than getting a newer machine. It was also very marginal for handling OS X.
3. iMac 24". In some respects, this machine has been the most reliable and the most unreliable Mac I have owned all at once. OS X has been a rock. I have experienced two application quits, none of which have brought down the OS, and have had only one issue that "hung" the OS, but it was while using Chicken of the VNC and experiencing a power failure. A reboot cured it. On the hardware front, everything is very solid, but there are a few quibbles. I can hear the dreaded screen whine and have a fan that seems to vibrate excessively. On occassion my Mac will sleep the screen and not the entire system, but it's pretty rare. Overall, I love this machine.
I wish my Windows XP box at work would be this reliable. Any change with USB devices will either kernal panic the computer, force a reboot, or reset my keyboard repeat settings. I have lost a drive, and had 3 power supply replacements. Overall, it's about on the average with every other Windows experience I have had.
The Mac isn't perfect, but it has been light years better than anything I have had on the PC side.