I've played Heroes vs Monsters on my 9 yr old's iPad, and it is a nice game. He bought it with his own money after seeing a friend playing it. It's a pretty nice little game with a lot of appeal.
It is obviously produced with a vector art program and appears to be 100% vector art, and if it were a Flash game, it would be obvious that it was all vector all the way through up to screen render at run-time. But since this is iOS, I know it isn't Flash.
The game works on iPod, up through iPhone 5 and full-size iPad. Obviously, it would be a great benefit if the underlying game engine accepts vector assets, and there is never any bit-map phase that you have to round-trip your graphics assets through, but I have no idea if there is such a framework for iOS. (The benefit being that scaling the GUI and mobs is pain-free, except where the developer might choose to actually provide more layout area on a bigger device.)
Performance wise, the individual elements of the mobs appear to be static, meaning the whole game simply treats the vector art pieces as if they are bitmap sprites. I need to play it again to see if there is animation of the elements that implies vector abilities, but the mobs are all basically a head, torso, hands, and feet. These 6 elements are merely translated and rotated for all the movement and fighting animation. Armor, helms, weapons, and such are mostly statically stuck onto the basic 6 elements (or replace them, as in 'plate-armor boots' replacing default shoes).
I did check out a YouTube of the game real quick and see that there is element squashing and scaling, such as when a bow is shot, or when smoke-cloud, flame, or dazzling-light effects are performed, but in the fight I watched, there was nothing I saw that can't be done in C2 with bitmaps.
I've certainly never seen any HTML5 system out there that rivals Flash for creating vector-based games. Adobe Edge is obviously meant to grow into that role, and there is a company called Sencha that produces something currently equivalent to Adobe Edge for use with their other framework(s) that could actually compete slightly with Construct 2 for making an HTML5 game, but it has nowhere near the ease of use and speed, or versatility of C2.
In my very modest opinion (meaning I wouldn't give my opinion a great deal of credence, but here it is anyway), given that it would be the first platform that would attract Flash game developers in droves, adding Flash-style vector creation and animation into C2 would be huge.
For me, that means the ability to create symbols that have their own behaviors, and, second, the ability to animate the vector art, but have it be interactive, not just static. As mentioned above, Anime Studio does vector animation very well, but making it interactive in a C2 game would be difficult, or more accurately, interactivity would effectively be limited to about the same kinds of things you could do with Spriter and C2, or actually not even that much, easily.
Flash can allow things like real-time game physics, i.e. gravity and collision, to affect the vector animation, since the underlying assets are vector right up until final rendering on a screen.
All this said, it would be nice, but I can definitely see this being too little gain for the amount of work involved. On the other hand, how formidable would the competition be from an Adobe Edge that was fully programmable and as capable as Flash is right now?