I use XP all the time and to say that it's unstable is just retarded.
I have an Duron 1100 MHz with 512 megs of RAM. I have a mouse, a graphics tablet, a USB joystick, a 21 inch monitor, a laser printer and webcam plugged to the computer at all times.
Does the computer freeze? Only if I use a TV card that wasn't certified for XP. Does it freeze otherwise? No.
I don't think any regular Mac user ever considers the fact that PC's are very regularly equipped with hardware that could be considered outdated. It's not uncommon to see a new computer equipped with a sound card that was released in 1998. Half the time, that sound card or any outdated hardware is the source of the problem.
When you want to upgrade a PC, you usually change just the processor and motherboard and you're on your way. When you upgrade an Apple, most of the time you're buying a completely new computer. It's obvious that if every single one of the pieces is approved by Apple, it'll work better. What would happen if Microsoft shipped its own PC's with only approved hardware of its own? Chances are it would never crash at all.
How many manufacturers make hardware that goes inside the PC? Several hundred. How many manufacturers make hardware that goes inside a Mac? You can count them on one hand, two to be generous.
When you're comparing a PC to a Mac, you're comparing a company that caters to billions of different configurations to one that caters to a few. If there is a conflict with Windows on a PC, it doesn't mean it affects every single PC out there. If there is a conflict on a Mac, it's easy to fix since every single iMac is identical and if you're using a tower, there are only a few manufacturers that actually make compatible hardware so it's not like you have to look for long to fix the problem.
Anyways, in the end, you have to hand it to Microsoft. They're not as pretty or secure as Apple, but they have a much bigger job to do and frankly, XP is a DAMN FINE os.
If there's trouble with XP, chances are it's the user's fault and not the OS'. Besides, if you were using a Gateway machine, you were using a machine by a manufacturer that equips its PC with the shittiest parts out there to make the biggest profit. I assemble my own PC's, as such I know I'm buying quality hardware. Quality hardware = quality experience and my XP is damn awesome to tell you the truth. Once again, it doesn't have as much eye candy as Mac OS X, but it's much faster and less expensive.