Pretty smooth API once it is wired up. I like the webhook pings for status changes, but I ran into a couple odd carrier responses that needed extra handling on our side. Not a deal breaker, just not totally plug and play.
Really happy with the tracking view. We hooked it up once and I like seeing updates from a bunch of carriers in the same place, without jumping around. Only nit is I had to tweak our branded tracking page a bit to look right.
Pretty disappointing and confusing overall. I tried to set up the tracking updates, but the webhook stuff was not clear to me and I kept missing status pings. The instructions felt too technical, so I may of done it wrong.
Rate it, and the next carrier reading this page sees what you found.