Gamma is a HTML5 framework I made for creating games. As an experiment I've used it to port two games: This Precious Land and HerpFortress. Also, there's a half-finished .obj viewer lying around somewhere, that's using it too. I have provided some thoughts on my HTML5 development experiences.

Javascript is fun until you need another source file. As the application grows, Javascript gets less fun. It is hard to keep a mental structure of the application when the code is so mutable. This seems to be the general consensus, as there is a large list of alternatives to Javascript. That said, Gamma is pure Javascript.

I used Google's Closure Compiler to provide a more sane development environment. It does this by providing namespaces and type annotations. However, namespaces cannot be imported, so you're left writting things out the long way. In the end, I guess the big-win is being able to statically compile to a single source file.

I do enjoy benefits of using a scripting language; specifically the read-eval-print loop. It means you can manipulate code at run-time, instead of waiting for compiles. This shortens the programmer feed-back loop, which can lead to new code discoveries. Also, it means iteration is quick.