There are three different discussions at play here that I think everyone is jumbling together.
1) Matterhorn and TSMM getting fast pass.
-Obviously this is going to be a disaster for their respective stand-by wait times. Selfishly these are two of the most aggravating stand by lines in the park. I personally can bypass Matterhorn with single rider, but TSMM is annoying even without fastpass. As it currently functions, it requires either rope dropping and losing out on the magic that is RSR single rider first thing, or waiting in a 30-45 min standby line. TSMM is always the longest ride I wait for in either park, there is just no avoiding it under the current system. Under the new system a fast pass should still be obtainable at rope drop and it's not like I would get on the ride more than once in stand by anyways. So personally it will save me the longest wait of my trip in either park. I'm a bit curious to see how it plays out though, DCA actually has a very high-priority Fast pass in RSR, unlike DHS which was TSMM or nothing.
Selfishly this will improve my DCA experience, but I'm sure it will hamper many others.
2) Electronic fastpass pick up
-This completely ignoring #3 is a good thing. This isn't the FP+ system, this is simply the current vanilla fast pass model without criss-crossing the park when your next window opens and back tracking to your former FP attraction. If anything, for what I would envision, I'd spend less time criss-crossing the park and therefore less time pushing through walk-ways. There is no denying that Fast Pass vanilla with paper tickets gravely changed guest flow and dumped people out of queues. An electronic delivery system, even if it was available to everyone, I honestly think will partially improve the previous damage by eliminating fast pass runners. Will FP run out more quickly? Perhaps. The convenience will allow more guests to adherently book another FP when the next window opens, but I don't see that change massively altering current distribution. I think the addition of a small number of FP via Matterhorn and TSMM would make up for that small bump. Minor changes to the FP window could easily be made if sell-out is truly impacted, which I highly doubt.
3) The 10 dollar cost
This I don't particularly get. You are paying 10$ for convenience. Someone up thread suggested the introductory price could be a way of soft launching the system without every single AP jumping on board day one. But the cost doesn't particularly make sense. $10 for wifi access as well? Ok, as a foreigner I'd see the value in that, I could avoid burning my data and paying my plans 5 dollar US roaming fee. 10$ for my FP solo convenience? I'd probably pay that too. 50$ per day for a family of five? Just get a FP runner. I don't understand the motivation for a cost. As people are worried about, the implications are potentially bad.