In moving my blog to Squarespace 6 I've had a lot of contact with their support service. They are 'just ok'. Yes, they have the usual boilerplate, "so glad you contacted us" and "i think I understand why this is important to you." Ok, ok. Enough cut and paste.
The problem is that they are probably pretty junior and used to answering easy questions. But when they get at all subtle or maybe even pointing to a bug, they are lost in the woods and give you useless help. But that's not the biggest problem.
The biggest problem is that there's no continuity. Each part of the support email 'conversation' is answered by some random other person. And while they probably make a good will effort to maintain continuity, it happens constantly that the new person doesn't understand what came before and gives you a non-sequitur answer.
Now I have nothing to compare them to, for example, what does blogger.com give in support (probably nothing) and what does wordpress.com give in support? (probably nothing.)