Here are my opinions of the games with gold games released so far.

• Fable 3 - Very well polished game. So, so very boring. Some games just aren't my thing. Some games are too difficult, or frustrating in other ways, buggy maybe. This is right up my ally, fantasy roleplay, and seems well put together. It's sheer blandness is why does it in. It's too streamlined, I guess? Got maybe 10 hours in before giving up.
• Defense Grid - Played a few levels, not really feeling it. I think I peaked with tower defense with Desktop Tower Defense. Nothing really wrong with this one though.
• Assassin’s Creed 2 - One of my favorite games this generation. The only Assassin's title I've completed. Loaded it up, found a few feathers, did one of the Assassin's seal missions. Still amazed at how great this game is. I probably won't play that much more, as I have Brotherhood sitting on the same hard drive. It's nice to have a digital copy though. At this point in the generation I'm sort of aggravated by having to find a disc to play a game.
• Crackdown - I'm not the only one who really likes this game am I? I've seen a lot of snark about it. I think this is a really great game and, like AC2, was happy to fire it back up and find some agility orbs. My agent is leveled all the way up so there isn't a lot to do without resetting all the bad guys. Still it was nice to bounce around the city again.
• Dead Rising 2 - Didn't really have much interest in this, as the frustrations I've heard mentioned with the series are exactly the kind of thing I don't want in my video games. But I fired up Case Zero just to check it out. I went through multiple cycles of hating it, being hooked, and hating it again, but ultimately I think I will try to finish it up. Probably won't touch the main game.

Overall I'm pleased with the Games with Gold program. These games are better than nothing. Even the ones I own provide the benefit of being digital.

Ironically, the program increases the value of my 360, and without backwards compatibility, decreases the likelihood of my getting an Xbox One at launch. (A small prospect anyway.)