The notion that Windows somehow sucks or is any less because of Microsoft's monopolistic ways is complete and utter BS. Yes, MS has a monopoly.. No, that doesn't make Windows not any good. It has NO effect on how good Windows is.
Depends what you mean by "good"
Their monopolistic practices dont make windows XP crash or difficult to use - but their monopolistic practices DO make windows bad for consumers in terms of choice of what they use and dont use...
An example is webpages coded to work for IE - if windows werent such a huge monopoly, then IE wouldnt be as widespread and web designers would be forced to follow standards which work for everyone - rather than making do with what works on IE and not even checking anything else