I am a loyal user of Spaces in Lion because with multi-touch gestures I find it a fantastic solution to move quickly between apps and especially between full-screen ones, which integrate perfectly with spaces. But something is missing, and that something is given by Yoink.
Drag and drop ... vitaminized
If you have the Finder on Space 1 and you want to take three files to a Space 3 app, the logical thing would be to drag them, but doing the gesture can make things very difficult for us, and this is where Yoink comes in.
Yoink appears just when we need it most as a drop zone, and it is in that area where we will drop the files and where we will recover them once we change space. Simple but vital operation at least for me.
It is sold in the Mac App Store at a reduced price for everything that we are going to use. We drag and drop files everywhere, believe me I mean it.