Their customer support is top-notch, they're always willing to go above & beyond for their clients in terms how quickly we can get an incident resolved or escalated within our org., They've got some really great tools that help us track down issues across multiple devices/apps at once (e.g using U2F keys).
I wish there was more transparency around what exactly makes up each tier so it's not just "1st line" vs 2nd Line Support when things are going wrong with them! That said though - 1) We use all tiers from time to time as needed; sometimes resolving problems ourselves but almost never needing second level assistance because everything works well together. Sometimes you need someone who knows your setup specifically. But if something goes awry then firstly it will be fixed very fast by one of those folks anyway.