"Flexible dyno hours" is some nice marketing spin. 550 hours a month works out to one application running 18 hours a day, whereas previously you could have an unlimited number of apps running up to 18 hours per day.
If you just want one 24h-app + a bit that's better, if you can live with <=18h for all your apps it is worse.
Before // After
18h for every app // 24h for one app
You just lost a huge number of free apps that could potentially become paid apps.
TLDR: Hassle of keeping track of account wide dyno use > hassle of running on vps