boy, it really depends on the classes. I got a lot more out of just finding other local mamas- which was very challenging, I was kind of out of the baby loop with my first one, and the first of my friends to have kids. I guess I'd just check and make sure the topics being discussed are topics you think would be relevant. I would suggest talking to the local midwives, or seeing if there is a doula organization where you are. They would be clued in to what is available and what would actually be helpful (I think the 'classes' I went to at a clinic had a lot of pop-culture & self promotion, not much mom-networking or practical/real advice) Check out your local chapter of La Leche League too- they are incredibly helpful, and you are bound to find supportive, caring friends there (who are usually quite frank as well and willing to discuss ANYTHING!)

Pull in that support network & do your own research- there are a lot of misguided (tho well meaning) folks with lots of BAD ADVICE that is hard to navigate through- especially hard to deal with from parents/in-laws since what our doctors are saying should never be done, they were told was necessary way back when they were having kids (like formula feeding and non-flexible shoes & so much more!)
Best of luck & congratulations!