If by BP you mean BuddyPress, my experiences with it basically boil down to WordPress not being designed to be a social network, so it doesn't do things "smartly" for a social network. While it is possible to turn it into one, the resulting resource load does tend to be over what our free hosting service can run, and I'm not sure it'd work particularly well on Premium once it got to a good size, purely because it's a blogging platform adapted into something it wasn't meant to be.
My best advice would be to switch to software designed as social network software; you'll still have the risk of tripping the usage limit, especially if the network begins to grow in size, but software designed for the right purpose will almost always work better than software adapted to a different objective.