1) I'm running an i7 4790K and a GTX 780. No way that random items disappearing out of my inventory, saves being corrupted, cutscenes refusing to load even after restarting the game, and random crashes (among so many other things) are the result of my hardware. I routinely run much more technically demanding games (modded Skyrim, Crysis, etc).
2) I don't actually know how Steam handles refunds, but I imagine it's not possible to get one and keep the game.
3) To the other question, this is the second game I would do that for; the first was Sim City, which was also unplayable at launch.
4) I honestly was thrilled for this game, and there's a good chance I'll come back to it in a couple months when it's working properly, but honestly it's such a mess right now I do feel like my money was badly spent. At the moment, I've played through the first part way too many times to want to do it again.
5) Looking at the tech support forums, there do seem to be a significant number of other people in the same situation.