After many years programming graphics in C++ I ended up having to code a big web project during a whole year, it was for the Barcelona World Race online game. Because the project requested lots of graphics and interaction I decided to do it in Flash, by that time I only had made some silly tests in Actionscript so I had to learn fast and not only the basics.
The project ended up being a success with more than 50.000 registered users (surprising for a game so niche as the sailing games).
After that project I felt that Flash was a great platform, performance is good, the API is complete, the official IDE has all I could expect, and the projects can be deployed to web or desktop without any problem.
Since then lots of people had jumped to the “HTML5 bandwagon” thinking that HTML5 is some kind of new technology but the truth is that HTML5 is just the regular HTML with some new media tags. The huge improvement is that now JS is really fast and powerful thanks to a mature set of libraries and APIs. Now we have a great web programming language which has everything you could need (HTTP Request, Sockets, Threads, Binary Arrays, Storage) besides the cool new media APIs like Audio, Video, WebRTC and WebGL.
Some people asked me where to start learning JS and I don’t have a good answer, mostly because the chaotic way I usually have to learn something new, jumping from project to project and testing in every one of them a new API. I do not trust books related to web development, they tend to be deprecated in their methods.
I made some slides for a seminar last year, maybe someone could find the useful, they are for learning HTML+CSS+JS but they are very brief.