Mobile: Develop for HTML5 and run it like a “native” app.
Geolocation API: Can use the users location for tasks that require that, ex: a Facebook check-in
Adoptability: Built around industry standards. Over 650 million devices HTML5 ready out of the box (iOS)
VS. Flash: Runs better than Flash, up to 58% better in some cases.
Fancy: You can do really cool things like parallax scrolling.
Development: Its a rather new standard, so will take a while to get robust, although it already is fairly stable.
Capabilities: Can’t render 3D content, and graphic extensive tasks very well.
Create: Not meant to create, meant to present.
Experience: Doesn’t have the years of dependence that flash at this time has.
Support: developer community is starting to develop, not as much as Flash had. Just a matter of time however.