To what? Windows or other flavours of Linux?
Although I've tried Ubuntu (and several others) I find that Mint just 'works' with my system and has all the drivers needed for my hardware and peripherals. Linux is certainly great as a free Windows replacement although I still use Windows more often due to certain programs being Windows specific. The only other bug-bear I have with Linux is that the look and feel, mainly the fonts, isn't seemingly as crisp. The fonts don't seem to render in a way that is pleasing to my eye!
Other than that I'd probably be more than happy to switch to Linux permanently.
I think Microsoft realise that there are many others feeling the same way hence the 'free' upgrade to Windows 10.