First and foremost, Corona SDK is lovely to work with. Lua's a great language, Corona's a very thorough framework, and the documentation's been great thus far.
In my opinion HTML5 game development isn't worth it yet. Both on desktop and mobile browsers. If your goal is to make an awesome game to run on desktops and mobile devices, then don't bother. If your goal is to make an HTML5 game, then go make it and use one of the frameworks people have mentioned (also look at Crafty or Gee for more of a drawing-type interface).
The primary reason is that when I make a game, I want to make a complete and polished game. Part of making a complete and polished game is good audio. Although the
<audio> tag is supported on major browsers (assuming you provide enough different formats), managing your soundtrack programmatically with
createElement is kind of a pain. SoundManager 2 is a band-aid, not a solution. In many cases it will just fall back on using a Flash object for desktops. At which point I ask, why not just make the darn thing in Flash?
On iOS, unless you use a hack like in Zynga's Jukebox library, you're actually limited to only playing sounds in response to user input. It's ridiculous.
Also, unless you're packaging your HTML5 game up as an app, people need a connection to play. The time I spend playing mobile games most is on the subway--no signal. And if you do package your game up, won't it be weird to not have sound? If I'm downloading a game I expect a certain level of responsiveness and polish. Read: a native app.
<canvas> and all that, but I will not go so far as to produce a polished game with it. It boils down to what your goals are. Very few I know who play games and are not developers even have mobile HTML5 games on their radar. Again, if you want to make awesome HTML5 games, make HTML5 games. If you want to make and sell awesome games, make the quality of your players' experience a priority.