I haven't yet. Have been thinking about the same though.
But I'm mostly worried that I will miss the laptop for work stuff.
My biggest concern are the screen size. A surface with a 12" screen feels small for the programming and drawings stuff I do for work.
When traveling it's mostly minor stuff you do though, so perhaps it's not that bad. At the office you can connect a proper screen so that's no problem.
The iPad is most for leisure stuff, browsing the internet and things like that.
Most devices should work for that. Perhaps not just as good though. I really like the iPad.
Also not sure if there is something to replace iBook. I use it to read books these days and I have no idea what's available for windows there.
The thought of not having to carry around that laptop is very appealing though so I think I will make the step sooner rather than later.
/SK