Had a game against Squats in the london event at the weekend, and must say those overlords were fearsome. Took an entire rough rider squad to kill the first, not to mention a hydra unit to prep them first, and the second took a unit walking over in it's general direction and plinking it. Crazy amount of force expenditure to take out a mere 1/6th of the squat army. Still, between them both they did manage to kill 3 rough riders and 2 chimeras before dying, so definitely still undercosted given that level of impact.
On a more serious note, overall i rather liked the list

The stars for me were the infantry units and thunderfire cannons, sadly for Steve he had some activation issues after i got a nice barrage on about 4 units in turn 1 with some manticores, and his Land Train never got a chance to do anything after i decided it looked scary and nuked it with my first activation. Yay deathstrikes actually doing something! For Steve i think the most frustrating thing (other than a mis-behaving cyclops, which just wouldn't activate after getting some BM's) was losing all 3 assaults on turn 4 - the first he was up by 1 too, but the other two, not so favourable, which cost him any chances of holding the game to a draw, and ended up a pretty hefty win.