I bought it during the same Amazon deal you did, loaded it, and said "screw this" after about 5 minutes of trying to get the controls to work, along with seeing the horrible console port. The port reminds me of Ninja Blade, only worse.
After playing 2-3 games for 2 hours or so each and finding myself "meh" about them all, then reading this thread, I decided to give it another go. I'm glad I did. I took time to try and figure out the KB+M controls, but after doing that for an hour, I concluded I wasn't getting anywhere and bought a wired 360 controller. It made all the difference in the world and I can safely say I'm really happy with the game, so far anyway.
Unless things change mid-game, I don't really see the game as unfair. I can account for every death I have had so far and see that my screwing up was the cause. There is little room for error, but I kindof like that, it keeps you on your toes and requires that you learn your opponents technique before rushing into battle. I feel like I've played games that are far more unfair than this (Ninja Gaiden, for example) and less rewarding.
There are some tedious parts, mostly the save/death system, but I think it would defeat the purpose of the game if you were allowed to save all the time. That said, I do find GFWL annoying and the interface horrible for a PC port. As mentioned before, the port itself is really pitiful, it blows me away that someone was paid to port this game to PC and did such a pisspoor job of it.
Anyway, I'm happy with it for $20. I'm not sure I'd pay more than that at this point, though. If they can make the PC port better, I'd probably say it's worth a more.