and to be honest, we've done it so many times before, and of course lots of software runs perfectly well on a Linux desktop.
To say that you can "safely say" Linux is "much better than windows XP" is incorrect - you can't safely say it, but you can offer an opinion. If that's what you think then fair enough, but millions will disagree with you. This whole question isn't one of which operating system is the best - the best operating system for you is the one that suits you the most, and that's all there is to it.
If you were running a software development company, and your potential userbase consisted of say, 10 million Windows users and 1 million Linux users, which sector of the market would you concentrate on? It's a simple matter of marketing sense - when there are enough Linux users to make it worthwhile for certain developers to see a significant advantage in ensuring specific compatibility it will happen.
Over the years we've seen the Linux/Windows debate rage back and forth, and each time we discuss the subject the arguments are much the same. Linux has definitely made inroads into the Windows market as time has passed, but progress has been very slow - the vast majority of home users still prefer Windows, and almost all new computers come with Windows XP preinstalled. Lots of corporate and institutional networks do run with Linux desktops, but they are still very much in a minority. Personally I couldn't care less what name is on my desktop; as long as the O/S does the job I'm happy, and I suspect that most people feel the same way. At the moment, and in my experience Windows XP does the job far better than Linux, so I'm sticking with it. I would take a small bet that a big majority of computer users will do the same thing, at least in the short to medium term. Software developers have their digital ears to the ground, and if there's the demand for Linux-friendly software they'll provide it.