None for print as I don't print. If I would, I can imagine buying a nice legible serif like Bembo
For screen I use Segoe UI, primarily for things like file listings, menus and the like. Anything I used to use Tahoma for in the past really.
Consolas is nice for coding (after years of switching from one font to another: Sheldon, Monaco, Lucida console, Proggy variants, Speedy, Triskweline, Andale mono, etc, etc. No Couriers for me, thank you).
Calibri for pretty much everything else.
After some finetuning using the ClearType Tuner I've become a ClearType convert.
BTW This (lengthy) Cleartype Team 2005
video from the past might still be interesting.
There's an explanation from appx 12:19 about Couriers typewriter origins. Also some info on hinting and from 32:18 on the effect the ClearType technology can have.