Played four of the demos so far, so will post impressions below:
Runbow - Honestly, I didn't expect much going in. Based on comments above, it sounds like some people didn't care for the single-player mode. But I was pleasantly surprised and found it kind of awesome to have a grid-based series of challenges that require you to race through levels and beat preset times to earn medals. The graphic design is bright and attractive, while game controls feel decent. Seems like multiplayer would be awesome, and online play is a great addition for this type of game. Despite being primarily a solo gamer, I'm now excited about Runbow coming out.
Verdict: Will Buy!Mutant Mudds Super Challenge - The name really says it all. Have you played Mutant Mudds before? If not, you probably want to start with the base game. Do you love Mutant Mudds? If so, this set of harder levels will probably be right up your alley. Me? I'm not really that into the series, and this game did absolutely nothing to change my opinion.
Verdict: Not For MeLovely Planet - Hmm... This didn't control well and seemed entirely pointless. It felt like a PC-based tech demo from an amateur developer instead of a fully developed game idea. Sure, the game is still in development... but Lovely Planet was by far the worst demo so far and I can't recommend the game to anyone. The only positive comment I can offer is that the art direction is different enough to be interesting; unfortunately they never do anything interesting with the colorful environments.
Verdict: Not GoodRive - Wow. I didn't know what I was doing and died quickly. Then restarted and did better. Then restarted again and really enjoyed it. Fast-paced, intense, interesting design. I loved Toki Tori 2 so had high hopes for this game... and it blew away all of my expectations. (Except for one: the demo wasn't nearly as accessible as I had expected, throwing you into the action pretty quickly.) There were some significant technical issues still to be ironed out, but I'm really excited to see this get released.
Verdict: Will Buy!Four demos down, and a better overall impression than I expected. Five left to try. From the remaining demos, I think that Extreme Exorcism and Typoman both look vaguely intersting - the rest I have no opinion about. Should be fun.