I played with 1 LBP level in the SF Vita Hill Club 2-3 months ago. It was a 2D top down physics based maze navigation mini-game.
My feedback to all is this:
Vita LBP may be familiar in create, play, share concept BUT it should be a very different game on a handheld.
PS3 is a physics and rendering monster compared to Vita. PS3 LBP is therefore a "realistic" tinker toy world. Vita is weaker but has more memory, touch screen, more social features and can go outdoor. Vita LBP should avoid direct comparison with PS3 and focus on Vita's strength.
The touch screen is intuitive but your finger will block your view if the level requires constant touching throughout the level. In the game I tried, I had to guide a SackBot throughout the maze slowly. My finger got in the way in tight spots. Over here, the back touch would be very helpful. I think new LBP mechanics to integrate with social sites can also be very interesting. Hope the developers spend as much time as they need to complete the Vita concept instead of just porting the same old PS3 formula straight.