Personally, the primary reason I want an R45 is the pup fits my hand (shape-wise, not size.) better than anything except my custom gripped revolvers, and the pup's not very far behind. That, and the pup's fantastic trigger, and overall build quality. Assuming they stick w. the pup, it should also be a much simpler (IMO = more reliable) design than something w. a manual safety, decockers, grip safety, etc. It should certainly make it lighter, and more compact.
And, hopefully, available w. carbon fiber grips...can't say I really like G-10.