I've read that HTML 5 is still a work in progress and not yet an official standard. (Although, the major browsers support many of the new HTML5 elements)

Is it then up to individual developers to decide whether or not they want to use HTML 5 elements on their websites. If a developer uses HTML 5 throughout
their site, is he/she at risk of limiting user experience for those with incompatible browsers?

Any thoughts would be appreciated.