I've covered a lot in the other areas, but they really are fantastic. I'm only about a month into working with them and I have an entire booking engine up and relatively smoothed out in every major way. Let me tell you... as someone who has worked in tech for a long time... that is not usually the case with something this detailed... I'm not a plug-and-play kind of operator either. I like to maximize the features available, so this is coming from a person who stress-tests systems.
Their customer service is SECOND TO NONE in my experience. They have direct API integration to all the major channels, tutorials for everything you need to build out your own site, API partnerships with tons of great 3rd party services and seem very open to integration with more if requested. Rolling out new technologies and upgrades constantly... This is the team I want to be on. Interactive and supportive.
Since their focus seems to be vigorously on functionality, 3rd party inclusion/API syncing, and constant growth within their own custom system, I would say the one issue they have is that while they focus on FUNCTION, they're less bothered by FASHION. Everything works beautifully (in my experience) but not a lot of the action behind the hood is sexy. It's like PC vs Mac. But I will take function over UI any day.