So, I've finished up Retro City Rampage today. The good news is that I played for about 12 hours and I enjoyed it a lot more than I enjoyed the demo. It's got a pretty brisk pace, a good amount of content, it's fun to just rampage through the city, I like the score attack mission rampages. It reminded me a lot of the kind of fun I had with the first GTA game. I also like that the city itself is fairly small, so you pretty quickly memorize where the things you want to go to are, which I like in an open-world game.
Now, that being said, it's not a great game. There are some pretty severe flaws. It's supposed to be a parody humour game, but most of the parodies are just references and puns. It's not absurdist or anything like that, it's just... I don't know what to compare it to. Like a bad video game Family Guy? I laughed every so often but I wouldn't call it funny on the overall.
The story is complete nonsense, every 45 seconds some totally random thing happens. Most of the story missions are fairly crummy as well--of the 62 missions I'd say there's maybe 15 that have interesting design. The final mission of the game an Outrun-meets-3d-world-runner clone that requires frustrating precision (this at the end of a 2d top-down GTA clone).
Also most of the stores in the city just sell character skins--this is a two-fold problem, one because there's like 10 stores that do only marginally different things and I kinda wish there could just be a menu that let you pick your character skin outright, and two because your character is like 8x8 pixels so most of the looks aren't really that interesting.
I did 100% the game--still working on the last achievement (edit: done!), but 100% in-game completion. I think in terms of recommendations, I'd say it's okay, but it's not a must play. I don't feel robbed for 600 msp, but I think holding off for a steep Steam sale might be the better way to enjoy the game. Almost no one bought it on 360, I'm in the top 100 of a whole bunch of the rampage leaderboards and in the top 20 of three or four--that's a sign there ain't many people playing.