Hi Dan,
You’ve got the concept right. Normally one would have to print the P2P target on the press with the linear curves in order to get your G7 curves - THEN - you’d have to run the press again using those curves in order to print targets for profiling the press, etc. What VPR does is apply the curves you got in your first run to the targets that you also ran in your first run so you can do all your curving and profiling with only one press run. The curving is applied to the measurements of your profiling target in the software. This can potentially be even more accurate than running the second press run (considering how inconsistent presses can be.)
Theoretically you could run all your different paper stock through on a single run, get the P2P’s and IT8’s on the sheet, and have everything you need on that single run to be calibrated to G7 and profiled. This is a big time and money saver for large presses.
As you say, if you do the job correctly - the closer you get to your standard, the more accurate the standard profiles will be when used for proofing. I suppose the advantage of VPR is that it will bring your proofs closer to matching the press regardless of how close your press is to the standard. Also nowadays, Curve2 is more than just G7. You can use it for other, customized references.
Regarding further explanation / training -
We uploaded some YouTube movies where Steve is explaining the functions of Curve2 and VPR. These go into it in great detail:
youtube.com/watch?v=jcmRfVDcRmk#t=01m07s