I put very beneficial, as even though I had already read a fair bit about labour and birth, they actually covered more than that. I found the classes beneficial in the following ways:

Familiarisation - getting to know the birth centre and the various midwives. Getting used to the parking in the area (which really sucked) and what services were available in and around the hospital
Hospital procedure - from having been on BB for awhile, I got the impression that each hospital/birth centre does things a bit differently, so it was good to know exactly when we were to call the birth centre, when to come in, why we could be refused birth in the centre and under what circumstances we would be transferred out and what would happen then.
After birth - the was a whole class on what happens after birth, what it is like with a baby at home (how long feeding takes etc), it was a real eye opener for all the couples. The best bit was a new mum brought in her 22 hour old baby and showed us how to bath her.

Downside - not very clear on the role of the support person, we learnt more about that by doing an active birth class.