No, if I ommit generaly bad experiences with Microsoft operating system, there are still concrete problems with lack of multitasking, file manager, bluetooth file transfers, USB mass storage. Using zune for administration is also problem, I doubt it'd work on Linux.
I've had an HTC phone before with Windows Mobile OS, and while it wasnt terrible I cant say it was inspiring or something that would make me want to buy another phone with that OS again. Never tried WP7 so cant comment on that one.
If Nokia were to produce another phone with Maemo on it (I know... it wont happen) then I would be interested, cause I do like that OS on my N900, would be happy to use it again.