I've seen it referred to as dystopic some places, though I never found it that way, and this is what Iain Banks had to say about it himself in a reasonably interesting recent CNN interview:

Iain M. Banks: Good grief yes, heck, yeah, oh it's my secular heaven ... Yes, I would, absolutely. Again it comes down to wish fulfillment. I haven't done a study and taken lots of replies across a cross-section of humanity to find out what would be their personal utopia. It's mine, I thought of it, and I'm going home with it -- absolutely, it's great.

CNN: What's it like, being a humanoid as part of the Culture?

Iain M. Banks: It's pretty great being a human in the Culture, with the drug glands and enormously long orgasms. You can change sex if you want to, and you have total control over pain, and blister-free callusing. That wasn't one of mine, that was Ken MacLeod, my chum and fellow SF scribbler -- "I've just thought of a good improvement for the human body: Blister-free callusing!" -- so I made a particular point of putting that in ...

Blister free callusing is something I'd welcome after gym this morning...