Wow!! Thanks! This makes me realize I have to think seriously about purchasing it if it’s for only one ride!!
Here I am, back in the room, so I have more time to weigh in on this.
I think it depends on a number of factors, including how crowded the park is, what attractions you most want to do, how you like to schedule your day, how many hours you want to spend in any given park, how much time and energy you're wiling to devote to making and remaking plans, and how much time and energy you're willing to devote to looking at your smartphone.
We're rarely in the parks into the late evening, so G+ times at 7 or 8 pm are not usually useful to us.
Today we went to DAK. At 7 am we booked G+ for KS for 11:10 am and ILL$ for FoP at 3:20 pm. At 10 am we booked NRJ for 4:40 pm. We'd already done KRR and didn't want to get wet again, but G+ times for it were still available. So we might've gotten 3 G+s out of it today. We don't ride EE and I've done Dino enough for the next year or two.
We didn't use G+ at all at Epcot, which we RD'd. Bought ILL$ for Remy, which we both thought was a waste of time and money. But at least now we know.
We're mostly using G+ so we don't have to stand in a long line at a favorite ride. If that's the only ride we can get G+ for, then so be it. WDW has gotten a LOT of our money this week. We'll add it up after we get home and I'll report back. It's not pretty.
When we went through the LL at KS this morning, I said something like, "We're victims of the Disney upcharge," and the two CMs at the tap points agreed. One of them said, "Truer words were never spoken." The standby line was 85 minutes long, so we were glad (I use that term loosely) we'd spent the fifteen bucks.
My unscientific impression is that G+ and ILL$ are making standby lines heinously long, worse than FP+ did.
ETA: When I say "fifteen bucks" what I really mean is $31.96, since there are two of us and it's $15.98 with tax. BTW, FoP was $14 + tax this morning = $29.82 for the two of us. Today's total upcharge: $61.78. If you divide that by the 3 attractions we did (KS, FoP, NRJ), that's $10.29 each per ride. Sheesh.