Personally i think that an IG armoured column is the harest thing in 40k as
1) Only anti tank or super strong troops can hit them
2)They can take on anything that the enemy can throw at them
3) And finally they squish puny xenos like tyranids and lost and the damned.
Although i wld say that when i c an opponent setting up Tyranids or necrons it does make me nervous anyway wats ur opinion