I guess it's just that I bought the most expensive Imac, the longest Apple Care Plan, Aperture, and some other software for spreadsheets, ect (which given all the problems I never bothered installing) and it's given me such a headache.
I've had a couple lemon Macs too. One of my Powerbooks had random kernel panics pretty straight out of the box from day 1. To this day, my 2008 MacBook Pro display zonks out on me sometimes, and I have to press a key combination to get it right. Never happens when running Windows 7 under Boot Camp, so I know it's a software problem. It's a known issue for Penryn Macbook Pros and has been since the beginning. Every time a discussion thread about this got to a few hundred posts in the Apple support forums, they would just delete it. Never got addressed, they just released another model.
My current iMac freezes all the time, but it put in 5 years of solid service and probably just has hard drive problems. Unfortunately, it's beyond my ability to replace the hard drive in this old iMac (newer ones are easy), which is a design flaw IMO since hard drives are generally the first component to fail. At least OS X is bootable from an external drive, unlike Windows.
Ever since upgrading to 10.7, my Macbook Air trackpad is unresponsive for a few seconds after waking from sleep. Very annoying. Even with their relative lack of hardware variety to support, the Mac OS is by no means immune to glitchiness.
Of course, PCs have plenty of problems too. I bought a top spec'd Dell XPS laptop two years ago which was an absolute bust. Complete lemon, which I promptly returned. I have a couple of their consumer laptops which have run well for years, and their business class laptops are rock solid.
Overall, I'd rate Apple computers as average in terms of robustness and dependability. Customer service is above average, especially if you buy Apple Care, but not quite on the level of Lenovo or Dell business.