The initial PRESTO rollout seemed quite fast. There was a long gap before TTC rollout started last winter, but that was all politics, not about the card itself.
Problematic? There was a glitch in the Ottawa rollout - but that's the only major problem that comes to mind. In the end I think it was a 6-8 month delay while they fixed problems with the readers in buses. Compared to the delays in other cities though that seems relatively minor, and there haven't been any similar problems in the other 10 systems.
Yes, it could have been much worse!