Unlike other frameworks with the same kinds of goals, HYPE doesn't put training wheels on the language. Instead it makes things easier and more consistent. For example, if you're working with time with HYPE, then it's a Rhythm - no matter what kind of "time" frame-based or clock-based. HYPE bridges the different APIs so that you have ONE way to think about time.
Josh and I aren't trying to save the world - we think HYPE is pretty cool and wanted to share. He's globe-trotting high-end designer and I own a software development company that does, well, just about everything. But we met back in 2001 at a Flash conference and the Flash community has always been important to us and our careers. This is our way of giving back to the very vibrant that helped us launch our careers.
As for the folks who see stability - I hate to say it, but I'm fairly sure that's a player issue. I'm kicking around Chrome with the 10.1 beta player and I'm not having any issues.