Err. It might not be very hard but it certainly is time consuming. And that for people not caring about windows.
If there were usable, regularly refreshed, instances out there'd it'd be slightly less bad. But this still by far the most annoying and intrusive platform to care about.
If someone volunteered to pay for the storage, I'd be prepared to make some time to create an AMI to reduce the startup time dramatically. Basically it would be "boot the AMI and start testing your patches". I'd even make it as friendly as possible for people who don't like to get too far from unix-ish environments.
Do you know about what it would cost? Could official community funds be used for it (it seems like something that is cheap, but which you wouldn't want to be forgotten about some month.)
Having an AMI would help, but even with an AMI in place, MinGW is still insanely slow. Running "make" on already made PostgreSQL (so there was nothing to actually do) takes 1.5 minutes. And a make after a "make clean" takes half an hour. This is on an actual desktop, not an AWS micro instance. So doing a git bisect is just painful. Is the MSVC build faster?