Well, it's been awhile since I played at my local store. Though, last I was there things seemed pretty even as to who was able to win and what have you. I was rolling necrons at the time and won a fair amount of matches. Whenever there was a 2x2 match these same guys (blood angels and tau) seemed to annihilate any others. Though, I think the tau player made up a lot of crap cause nobody else played em. If I had to pick an army that seemed to get spanked more than others it would be the eldar, but I don't think the guys that played em knew how to use em very well.
"There is a cancer eating at the Imperium. With each decade it advances deeper, leaving drained, dead worlds in its wake. This horror, this abomination, has though and purpose which functions on an unimaginable, galactic scale and all we can do is try to stop the swarms of bio-engineered monsters it unleashes upon us by instinct. We have given the horror a name to salve our fears; we call it the Tyranid race, but if it is aware of us at all, it must know us only as Prey."