Todd: As a fellow Platinum, I've booked many tickets for my wife and a few freinds, and never have any of them been treated specially or allowed an upgrade.
Several statements to my wife regarding the opportunity to upgrade have all been "we'll your husband knows there is a first class reward, why didn't he book it."
Overall the ability to override some capacity controls makes it all worthwhile.
I also agree with the fact that many CO reservation agents don't know or understand the international upgrade procedure or what fares will work. A case in point was my return from LIS on a 757 being told no Bfirst availibility to find two open seats. Not a happy time.
Here's another interesting one: I tried to upgrade a buddy of mine on LAX-EWR a couple of weeks ago. The first flight that day showed two or three people in first one day prior. After speaking with the elite desk I was told that there was no way to process the 10k reward electronically, that it required paper cert's. Go figure.