I like that they are able to customize an entire solution for us, from design/branding all the way down to implementation and support.
They have been very responsive throughout each stage - when we were first looking at it as well as during our migration process which included multiple iterations with them due to some initial difficulties they had resolving (which was resolved). The pricing is fair but not cheap either. We're still getting used to having such complete control over everything related to IT services so there's no real downside yet except perhaps learning how things work!