Wow...well, that exact "detailed" response is what i've generally seen in most Apple related threads whether or not it is actually relevant to the question in a true sense.
There are thousands of Apple developers and Software engineers who absolutely enjoy the platform and have been churning out some amazing applications for years. There's a reason why the annual Apple Worldwide Developers Conference generates such a staggering response every time, the event has been a sell-out for the last 2-3 years, developers/designers love working on the platform.
But at the same time, no platform is 100% trouble free to work with, and then some 3rd party applications, largely due to their own shortcomings fail to retain compatibility across OS versions but labeling the OS unstable for that, is ignorance.
In fact, Mac OS X is largely popular and loved because users find it much more stable and trouble free to begin with.
Calling Snow leopard a "supposedly tweaked and UI improved version of Leopard" is again an understatement by a large extent. Snow leopard actually incorporates a massive rewrite of apps into 64-bit Cocoa(OS X's native API), Apple went through close to 90% of the OS code, re-factoring, improving and adding new advanced technologies like Grand Central Dispatch and Open CL, native Exchange support and many other noticeable performance enhancements throughout the OS.
Apart from a few remote issues which Apple seems to have acknowledged and working upon, Snow Leopard is a good release and it has generated a fair share positive response/reviews.
Now to answer your actual question, would you just buy something because its cheap and "works" or do you care to look if its build quality is any good or if it would withstand rigorous usage overtime. Its a fact that quality always comes at a price and Apple hardware is just that.(read my previous posts)
Both hardware and software are equally significant to Apple, which is why it makes Mac OS X software for its hardware lineup.
Apple cares more about the
user experience and
innovation rather than using the latest and greatest GPU in their machines which may or may not be actually required by the user and their formula seems to be working
great.
And once again, comparing PC desktops to iMacs is nonsense, because an iMac despite being a "desktop" machine is an All in One.
Instead, pick an AIO from Dell and then do the comparison.