It's strange that we have both very much opposite experiences. I'm not sure what you are using when you mention "linux" because responsiveness depends a lot on the distro. I wouldn't use Ubuntu, for example. As for Firefox, I guess it depends on your config/RAM/processor, but i have a i5 with 4 gigs of RAM and opening Firefox with saved tabs is slow as hell on Windows 7 while much faster on OpenSuse. By the way I'm using KDE and I don't think it's that bad in terms of stability, while I have experienced a few crashes (maybe once a month or something). It's true that Windows (from 7) has become very stable, nothing like what XP used to be: it does not crash to blue screens anymore, but it still can become very sluggish when I do audio/video editing and basically nothing much runs in parallel because it's just unusable.
It is strange. I've used gentoo for years, arch, debian, ubuntu and probably others variously. All pretty similar experiences though I agree on ubuntu.
