Interesting to see a new game creator coming about, but it's still very thin on details of the creator application itself. The StencylWorks page now says it's directly inspired by Scratch - is that an edit since you guys saw it? Still, I'm a bit disappointed since I always thought of Scratch as being an educational tool or toy (no disrespect meant to the Scratch folk though, looks like they're doing a good job). Stencyl might fall in to the awkward system of having a rudimentary event system with scripting for everything else, like GameMaker (where I think the pros consider scripting the only decent way to make games).
The games from a technical standpoint seem very simple and since I'm used to V-synced floating point scrolling, the Java scrolling looks pretty shakey to me. (if it's software rendered that's going to be hard to fix)
The java/web-play system is cool and we don't have anything like that, but Multimedia Fusion does now, so I think they'll have a tough time persuading any MMF users to move over, especially considering how simple the games look.
I still don't like their secracy. Their entire userbase is incredibly overhyped, so I wonder how much down-to-earth reviews they really hear.