I've tried this, and the delete "button" is ghosted and will not delete (plus, I've already experienced the pleasure of iTunes automatically - and unwantedly - deleting over 4,000 photos from my replacement iPad when I first hooked it up to my new MacBook Air).
Deleting was a piece of cake on my previous, non-iCloud iPad 2, but now I am not (yet?) able to do it.
I do NOT want the answer to be that I need to delete them on my MacBook Air and then Sync - I want to view and delete on the iPad (it's my wife's iPad and her photos - and I don't wish to keep the photos on my MacBook Air).
I don't want my Apple products to be adding and deleting photos automatically (or whatever), I want to do these things manually. I'm sorry to say, as a loyal Apple user since 1985, but - man - sometimes I HATE Apple! (The imminent death of the MobileMe Gallery is just another example...)
Anyway, any help on this would be much appreciated.