> Well, VS 2010 is probably a multi-GB download and install. Besides,
> having to juggle between two different VS versions will quickly become
> confusing.

Sure. However, it is not feasible to keep the build systems for many
VS versions up-to-date, just because contributors are shy of installing
the current version. Tracking two build systems (autoconf and VS) is
already difficult enough.

> Speaking as a non-native Windows developer, there are enough hoops I
> must jump through to do occasional testing under a Windows VM. So I
> might simply stop caring.

This is free software. If you don't want to care, you don't have to.
It's the same as switching from Subversion to Mercurial: we probably
lost some contributors who never bothered to learn Mercurial. That
didn't stop us from switching. I expect that most occasional contributors
will find it easier to use VS 2010 than VS 2008.