This news actually broke a couple days ago, but whatever: the latest (or nearly so) word from GOG is that they have brought Windows 8 support to 431 games in their catalogue, which is about 90% of what they have available.

…as of today we’re adding official Windows 8 support for most of the games in GOG.com catalog. There are currently 431 titles fixed, tested, and reported to be working properly under Microsoft’s new OS. Note that most of these have not had the master builds updated, so you shouldn’t need to redownload the installer or anything. Some of the titles, our build ninjas performed their usual magic on, and they’ll work now in Windows 8 — and we’re even adding Windows 7 support to a few. We’ll also be adding more Windows 8 games as time goes by and we’ve got time to apply some fixes to more of the classic games in the catalog.

You have to actually visit a game’s product page at GOG to see whether or not it is listed as Windows 8-compatible; you won’t find that information in your list of owned games. So, for example, the Ultima 4-6 bundle is Windows 8-compatible, and…okay, I can’t find an example of a game that isn’t listed as such just yet. Whatever.