Stewart Gleadow (@StewGleadow) and I did a quick presentation at Cocoaheads this month highlighting some of our favourite (or more obscure) Xcode 4 shortcuts.
The main take away of the whole exercise for me was finally memorising the shortcut symbols. This has vastly improved my ability to remember new shortcuts. I suggest you do the same!
Stew has posted answers to some of the questions over on his blog.