where can i download pss demos and how to copy it to my vita
They're included with the ps suite sdk. They install at Libraries --> documents, so that's where to find them
You also need to install the App that runs the demos on the Vita itself. You do this visiting the same page you downloaded the sdk from with the Vita's browser:http://www.playstation.com/pss/develope ... dex_e.html
From there you need to open the demo with the sdk (.sln file), open the dev app on the Vita then press F7 (that builds it), and then select Run --> Run With --> PS Vita to upload it to the Vita.
It's pretty easy, I was pleasantly surprised.
A question myself, how do you delete uploaded files off the Vita dev app? There doesn't seem to be any obvious way to do it.