SpiderFighter: Sorry for taking us off course here, but I wanted to say thank you for posting your thoughts; this is definitely something I'll want to pay attention to when making future purchases.
Each gamecard tells for which Windows releases GOG guarantees compatibility and support. I think they have said that if the game is playable on all their test PCs with that Windows version, it gets approved. If it fails even only on one, it will not be marked as compatible, even if it worked on all other PCs (with the same Windows version).
If a GOG game is not marked Windows 8 compatible, I think usually it means either of the two:
- GOG hasn't fully tested it yet on Windows 8 (on all their test systems).
- The game has severe issues on some Windows 8 configurations, not necessarily all.
That said, I am personally aware of one GOG game that apparently flat out refuses to run on Windows 8, while works fine on Windows 7: Haegemonia Gold. It works fine for me in Windows 7, but when I run it on the Windows 8 partition (of the same PC), I recall it just crashes after intro, when it was supposed to go to game menu.
Other users reported the same, I haven't so far heard anyone successfully running that game (at least the GOG version) on Windows 8. When I contacted GOG support, they confirmed there are problems with Windows 8 with that game, and that is why they haven't marked it compatible with Windows 8, only Windows 7 (and below).
I am unsure if Robin Hood is a similar case, or if "JustADreamer"'s problems are about something else. I might try it, I have a perfectly good setup to test if some game runs the same on both Windows 7 and 8, as I have both installed on the very same system, use the same driver versions etc.
Anyway, Haegemonia case clearly shows that it is quite possible for some game to be compatible with Windows 7, while failing on Windows 8. So apparently they aren't quite as much alike as some have suggested, as in "any game that works in Windows 7, will surely work also in Windows 8". Maybe that is true 95% of the time, but not quite all the time.