Thanks for everyone's help - it's a great starting point.
However, the more I think about it, the more I think it would be useful for tighter integration and more feature sharing between PS and LR. So, PS could really do with an improved print menu - including output sharpening and other things which LR offers. And some of the colour etc adjustments in LR (and RAW) would also be very useful - especially with the ability to use masks.
And, on the flip side, it's incredibly annoying not having soft proofing in LR - especially if you want to tweak for final printing in PS then print in LR.
No doubt the two products will evolve increasingly together - it will be interesting to see the evolution.