I agree, great game and I can't wait for the full version. Unfortunately I can't get the editor working and was wondering if you'd care to share some of yours?
Hotkeys for level editor are given on the game page.
Some of them don't seem to work, I just tried every touch on my keyboard until I figured out which does what.
I think TAB opens the menu where you can choose which tool you want to use (aka: which game element you want to clone somewhere in the level).