Early game, I like to make use of vanilla mob spawner mechanics and mod added abilities to pick up spawners (force wrench, gravity gun, portal gun, etc) to build vanilla-like mob traps. Basically 9x3x9 space with a spawner in the center, except I usually do multiple spawners so its more like 11x4x11 (full encloser being 13x6x13). Instead of water, I use conveyor belts to funnel mobs into a 3x3 pit that drops 12 blocks below the encloser so that I can stand close enough to the spawners to keep them active yet have the mobs die far enough away from the trap that they won't prevent further spawns. Instead of a crush, drown or gravity trap, I use conveyor belts to shove mobs into upside down iron spikes at head height. The same conveyor belts ensure drops go into vanilla hoppers that funnel into the collection chest.
Later game, if I really need a mob trap later game, I'd snag the specific mob I was looking for in a safari ball and add in an autospawner to the above trap. It's always nice to have a vanilla or soul shards spawner in with an autospawner to take care of the mob essence. However, I'm given to understand that sewers will be able to collect exp orbs as mob essence in a future update. If so, then one's meat factory can also fuel one's autospawner. Also, if I'm reading NEI on this update correctly, liquid meat becomes a fuel; making possible a power system based entirely upon deliciousness.