I ask because I use Windows pretty much as just a "dumb terminal" OS on a couple of home/office systems now. Outside of programs that I have that I can't get Mac versions for (or don't care to pay for another OS version), it's basically just used to perform very utilitarian tasks these days. Once I moved to the Mac OS about a year ago, most of my efforts have been devoted to becoming a more knowledgeable and effective user of that OS.
To use a car analogy: I have an old '84 Chevy pickup that I use to tow my race car and haul cinder blocks and firewood on occasion. It has a carburetor, no onboard computer and an engine that I can personally work on. Rather than get a new pickup that I can't work on, I'm wondering what the opinions are of the new Jag XK, and whether it might be a good replacement for my aging XK8. That's the car that I actually use for long road trips and the one that I would replace. Like Windows (in my case), the old pickup serves its purpose well enough. But if I could find a deal, I would ask the owner of a new XK what he thinks of it versus an older XK8. That's totally unrelated to my preference for the old pickup over a newer one. Better?
Sounds like you like Mountain Lion versus Lion well enough? No major issues?
Ah, well there is certainly nothing wrong with XP for getting the job done. It has done a great job of that for over a decade.
As for Mountain Lion, no issues. Though Windows is my main OS. I use Mountain Lion and Lion for iOS dev and Mac web app/site dev testing to make sure I cover many OSes. Other than that, I don't use Mac for the majority of my work or play. But for the development and testing within both, I haven't had any OS issues.
If you have a desktop Mac, I would do the upgrade. If you have a laptop mac, you might want to find a mac forum to ask about battery life as I have seen some benchmarks showing a large drop in battery life moving from Lion to Mountain Lion. Which may only affect certain models and might even be resolved by now. But just to let you know that it can affect battery life for mobile devices.
