2.) There are two Surface models, one is the Surface RT (which this article is talking about) and the other is the yet to be released Surface Pro.
The Surface RT is slightly heaving than the latest generate iPad.
The Surface Pro is supposed to be 2 lbs., which is lighter than the smallest Macbook Air and with the exception of form factor, it is every bit a real computer as is the Macbook Air.
3.) There is no start button in Windows 8 or Windows RT, so I don't know what device you were demo'ing.