I've been focusing on lists built around the Swarmlord deathstar and the results have been good. The Swarmlord unit is 410pts and it can take on units almost twice that cost. Another benefit of having the Swarmlord is that he unlocks hormagants as a viable selection for competitive play. The hormagants provide the 4+ cover save for everything behind them and the Swarmlord can give them furious charge, preferred enemy, and/or paroxym whatever the hormagants charge into. This combination has allowed the hormagants to defeat thunder wolf cavalry in close combat multiple times.
HQ - Swarmlord, 2 tyrant guard with lash whips = 410pts
EL - 3 Hive Guard = 150pts
EL - 3 Hive Guard = 150pts
EL - Doom in spore pod = 140pts
TR - 16 Genestealers = 224pts
TR - 10 Termagants with devourers = 100pts
TR - Tervigon, adrenal glands, poison, catalyst = 195pts
TR - 15 Hormagants with poison = 120pts
TR - 15 Hormagants with poison = 120pts
HV - Trygon Prime = 240pts
It's a good list. Recently I have been toying with the idea of removing the Trygon Prime. The Trygon Prime has been the one unit that underwelms in this list. It only seems to do well when I'm winning and the game is in the bag. Otherwise I get nothing from it. The Trygon Prime is in this list for several reasons.
1) It provides synapse and shadows coverage in the enemy backfield
2) It is my best option against Land Raiders and Monoliths
If I take it out I am really giving up on #2 and in my mind I must find a replacement for #1. 3 synapse creatures is the bare minimum in a list like this and planting a shadows of the warp in the enemy backfield is key against most Grey Knights builds.
My first thought was to replace the Trygon Prime with another big unit of Genestealers. Those guys are good in here and I could use another unit. But my shadows control will be hurt big time with only two shadows units. The Hormagants benefit the most from synapse control so if I removed them I might be able to go with only 2 synapse creatures. Bingo the 2 units of hormagants became another big unit of Genestealers. Without the hormagants, the Swarmlord unit would be hard pressed to get cover saves so I might as well remove that and now the whole list is changing. Without going into any more of the sordid details this is what I came up with.
HQ - Tyranid Prime, twin boneswords = 90pts
HQ - Parasite = 160pts
EL - 3 Hive Guard = 150pts
EL - 3 Hive Guard = 150pts
EL - Doom in spore pod= 140pts
TR - 16 Genestealers = 224pts
TR - 16 Genestealers = 224pts
TR - 14 Genestealers, Broodlord with talons = 244pts
TR - 11 Termagants with devourers = 110pts
TR - Tervigon, adrenal glands, poison, catalyst = 195pts
TR - 20 Gargoyles, adrenal glands, poison = 160pts
What have I done?

All I wanted to do was replace the Trygon Prime, but now I'm adding in over 50 models to the list. I don't know what to do at this point.