when the 720/PS4 come out with D11 capabilities, you will see a boom in it's use.
I hope it will be at least D12 ;)
To the question- i think currently developers are used to parallax/normal mapping pipeline that in some way simulate tessellation,
also when you turn it on changes aren't so breath-taking. (mainly because currently it's just for having cool statement on the box)
currently you can see real potential only in some tech demos...