I find it amusing how everyone bitches about Windows and it's constant crashing or the like. I heavily mod games and play around with the settings of PC's and laptops, I've grown up with a PC (I'm 19; one of the wonderful "tech" generation) since 1995 and I've never had a blue screen, or an error so bad I've had to call someone else. I've always been able to fix anything that happens.
I will happily grant you that I have had no issue with Windows 7. None at all. I think it's a good operating system and I quite like using it; although there are things I would change. I use Ultimate 64 on my Macbook Pro and have done for about a year. Not regularly but occasionally. I have no major complaints and I like what Microsoft have done with Windows 7.
OS X 10.7 'Lion' isn't perfect. There are things I would change and I don't think the App Store program is particularly well written (or useful). iTunes I find bloated but generally works well and when I had an issue with a movie I downloaded a few weeks ago ('Some Like it Hot' if you're interested) and I couldn't re-download, I emailed customer services and within two hours had sent me a special link and the problem was fixed - although it was originally an iTunes problem; it's not perfect.
I do find Lion works better for my day-to-day use than Windows 7. I've also used (and liked) various Linux flavours and although Ubuntu can be a bit of a hassle it works well mostly.
I have, in the past however, had some really deep underlying issues with Microsoft software.
We used to have Windows 95 (many years ago) and it was quite unstable. BSOD quite often and frequent spontaneous restarts. NT4 was good (I used it at school) but was never compatible with anything. XP started badly and got a lot better after SP2 - before that it was unstable and buggy and very easily susceptible to malware (from running by default as a root user - big mistake and this was fixed in Vista). Vista started badly too and unfortunately was promoted to run on hardware that it should have never been intended for.
I always used to worry about the 'Vista Compatible' stickers on laptops because that meant that Vista would
just about run. On my brother's PC (an expensive one!) Vista runs just fine but the minimum hardware requirements should have been much more stringent.
Windows 7 has solved most of these issues. No problems.
In the equivalent time, I haven't had any problems with an instance of OS X. I've used 10.3 a bit, 10.4 a lot, 10.5 a fair amount and have extensive experience of 10.6 and 10.7. They've mostly been improvements (I think 10.6 was the best all-around) but I've never run the operating system and run into genuine, real frustration. Apple have consistently put out well-polished software that's free of many major bugs (of course, many smaller ones still exist). Microsoft have regularly put out software and then had to put out major 'service packs' to make them palatable and stable.
This is partly because of Apple's vertical integration (system, hardware and marketing) allowing for relatively easy system compatibility. Microsoft have a much harder time of it because they have to allow compatibility with dozens of hardware manufacturers and inevitably cannot test some configurations properly. This was much more of an issue in the past and Microsoft have addressed it well in recent years. Windows 95 and 98 were terrible for this particularly, as was Vista. The less said about ME, the better.
So where do I lie? Well, I've made it clear that I'm a daily Mac user and have been since 2006. I prefer using OS X for day-to-day tasks and the software I use for daily productivity is very stable and simple. I use Logic Pro 8, Max 5 (also available for Windows with less community support) and Apple's Office Suite (which is very decent and I think more elegant than MS Office). If I didn't have these things available to me, I would use the Windows 7 equivalents. I'd probably be fairly happy too.
With that said, there is little on the hardware side (that is significantly cheaper) that is as impressive as Apple's
overall package. The build quality is excellent. The industrial design is superb. The specifications are generally lower than the price equivalent Windows PC but that rarely takes into account the quality of the display - which is absolutely top-notch. The screen on my Dad's 21.5 iMac is just beautiful and would easily be £500 if bought as a monitor. The 15.6" screen on my Macbook Pro is fantastic and I value a good display over a couple of hundred MHz personally.
I'll also say that Apple's customer service has also always been superb. A couple of years ago my Dad had a problem with his old (2006) iMac. The display was malfunctioning. Although the computer was years out of warranty Apple acknowledged that there had been a fault with his batch and it was repaired free of charge even though the machine was four years old at the time.
The nearest equivalent to this experience I can think of would be buying a good Vaio laptop or a top-end Lenovo. I love Sony's laptops and I think Lenovo (and IBM, before them) make great machines (although on the Lenovo I couldn't swap the keyboard out for Dvorak like I do usually). I have a 1998 IBM laptop (that a forum member gave to me, actually) that is very impressive for a machine of its age. Beautifully made and I know that Sony and Lenovo still make laptops like that when you pay serious money.
With that said, if I'm paying over £1,000 on a computer I'd rather take the OS I prefer all else being equal. I prefer OS X although I will acknowledge that Windows 7 is a very good OS. My experience with Apple's Customer Services has always been highly positive and that also adds a great deal of value.