I personally think that HTML5 will cause a lot of problems, which will be pretty similar to the problems we allready have with IE6 .
First of all, it will take ages before you can really develop complete websites in HTML5 , as a lot of user probably won’t upgrade to a HTML5 -compatible browser any earlier than 5 years from now. Just take a look at how many people still use IE6 !
Second, there wil probably a lot of issues with browsers rendering HTML5 just a little different, which will cause HOURS of debugging for sure. Although closed-source (like Flash) is sometimes considered bad, in this case it really helps to prevent compatibility issues (which is probably one of the biggest advantages Flash has over HTML5 ).
Alltogether I don’t quite believe HTML5 will be any great succes for the first few years from now.

I just hope it’s only bad luck.
