I also like the separation. I'll frequently check over there, to see if anyone is looking for an item that I might have, but wasn't thinking about selling.
I do think though, that it being a bit more hidden is causing lower traffic to it. I would almost suggest a drop-down menu off the "sell/trade" tab. (Make it B/S/T again). And you can either choose "buy" or "sell". A lot of internet users are too lazy to go search for the "buy" forum.
And yes, I know it's in quicklinks, but I NEVER use that unless I'm going to the WTB forum. And I'm sure a lot of NS is the same.