Looking at the spec, I see a few good ideas and a lot of crud thrown in. There are a few very nasty bits also where they change subtle bits of behavior, such as altering the OnChange event slighly. This is liable to break existing web sites when the new browser shows up and fires off unexpected events.
There are some good ideas in the lot though, the input event would be nice. Fixing the layout on TextArea has needed done for years, as did applying MaxLength to all fields where it makes sense. Some of the controls they suggest would be helpful, such as a date field. And the ability to submit a form and then update it without loading everything would be very usefull for complex applications.
Most of their control suggestions could be done in javascript. But writing the javascript for complex fields can be very nasty. On the other hand, their additions to limit ranges and submit numbers in a different form are fairly pointless. The first is easily done in Javascript and the second should be handled as a server side issue.
Jay