Simply do a .zip file…
or link to dropbox or google drive 
To answer the main question from my point of view:
- the feature i will use most often: undo
- the feature i consider the most powerful: global rackspace
But there is so much more to look forward to…
I’ve been waiting for this Global Rackspace from the day I bought GP3. I use a small set of VSTi (B3, Rhodes, Acoustic Piano) in nearly 80% percent of my rackspaces/songs and memory usage as well as startup/loading times will increase every time I add a new rackspace/song. So great idea, I’m very excited about this!
But why not let multiple Rackspaces be something like a sub rackspace capable of being included in the other main rackspaces? And why not let rackspaces include sub rackspaces including other sub rackspaces… ? Doesn’t it make sense at least up to a depth of two or three levels? Why are you stopping on this path after making the first step?
But finally one question: Does the global Rackspace support audio input and output only or also midi? Also up to 64 in and out like with audio?
I just read about some other new features like undo and others, very welcome! Can’t wait doing the upgrade!