With Windows, I've found that driver support often halts once a manufacturer has provided it's obligatory release. I think this is a limitation of the commercial closed source model that Windows (and OS X) follow.
I think an open source model encourages iterative improvement which isn't tied to commercial product releases.
I agree with you that open source model should (and often does) solves problems with hardware support, at least in theory. Then again, my bluetooth on linux simply refuses to work, no matter what I do (while on the same hardware windows never had any problems).
Your original comment was a little bit ambiguous: you were primarily thinking of legacy hardware support as in "legacy hardware support is often ongoing". I read the first part of the sentence "Problems are ironed out" as if that's only valid for linux, which I don't think it is.
I think an open source model encourages iterative improvement which isn't tied to commercial product releases.
This was the basis for my comment.