What i found so discouraging about the Battleforce is that it only gives you troop selection (unless you use "alpha' warriors). Its a kick in the butt from GW and there are no new Tyranid kits in it.
I think its a sneaky way for GW to make more money off the new tyranid players because they don't provide them with any Heavy support or fast attack (one of those kits is usually in a battleforce).
The way the codex rumors are going, it sounds like we could have complete "nidzilla" army lists consisting of hive tyrants, trygons, broods of carnifixes and warriors as troops taking out the need for anything on a small base (except for gargoyles which are cool and is almost every nid player's dream).
In conclusion the swarm army build might be up against a nidzilla army build that we have never seen before, so GW might be trying influence players to try and play Nid swarm by just having troops in there battleforce