Some things I think should be improved asap:
Grid: Is a button to turn a grid display on/off too much to ask? (don't say just use enders. It should be in the default client.)
Placing items: It would be nice if you can place items where you want. It seems to be working on items you build, but after that when you lift them up it doesn't. Well actually it does sometimes, like it is randomised. This should be easier to do!!!