I think a lot of people feel betrayed because they've lost what they saw as a great deal -- lots of rides on the headliners with little waits at no extra cost. Hard to trust a company when you see it as having just betrayed you.

But I think it'll work out fine as well. People who do their homework will always have an advantage over those who haven't, and there'll always be ways to tour WDW more efficiently.
But at the same time,
I do think people who used FP- heavily are not going to be able to use FP+ the same way, and they aren't going to be able to take multiple rides on the headliners without more waiting in line. I wouldn't be surprised if Disney fiddles with FP+ or that removing tiers off season or adding more FPs per person is part of that fiddling, but no way is it going to match 6-9 FPs on the headliners a day at regular
ticket prices. That can't be done for everyone, so it's not going to be possible for anyone.
OTOH, paying for extra FPs or getting more FPs depending on where you're staying are certainly possibilities Disney may roll out, I dunno. I don't see Disney having any problems with people buying multiple tickets in order to have more FPs in the same day, either -- even if people who do that spend less on food and souvenirs, that's likely balanced out by the cost of the second ticket. There'll be work arounds, for sure, they just won't be free anymore if you want multiple rides on the headliners.