I came from using GameMaker Studio, so porting my game wasn't straightforward, but that's the fault of GameMaker and not StageXL.
Part of the reason I chose StageXL was because of Dart. I've never been a more productive, happier programmer than when I'm using Dart.
I'm using Cordova to wrap my game and distribute on the app stores and it's been a breeze to write a game that works well on both Android and iPhone.
I'm super excited to start using v1!
Feats: Responsive Layout, Canvas2D fallback for slow mobile devices, Material Design Components, Google+ and Facebook integration, Physics engine (experimental port of Box2d), Wrapper for BabylonJS, StageXL Runtime Examples: BitmapFont, DragonBones, GAF, Spine, Particle, Flump
Bonus, port of FlexBook: http://rockdot.sounddesignz.com/stagexl-commons/experimental...
(no touch support, yet)
It's at v0.6, so be kind.
Edit: Animation run at 60fps and look smooth because those animations are using bones and key frames. The runtime interpolates the motion of those bones between the keyframes.
(disclaimer: I work on the Dart team at Google)
Part of that is just because of how versatile it is; it's not just a web programming language. It has multiple uses from mobile to web, back to front end. In fact, there's even a new OS where it's a first class citizen.
Watch some of the videos from the recent Dart summit and be amazed!