i use them a lot, units of 5 are usually best. i equip them with with 2 meltaguns and a power fist, the ultimate tank poppers. turbo boost them first turn into cover, then go tank and transport hunting, they can be nasty in combat with the mark of khorne and a power weapon, i took out 5 terminators with them. shot with my meltaguns, killed 1 of them, then killed another with T-L bolters, then charged in and killed the rest with my 4 power weapon attacks mixed with my 12 ccw attacks. they work as a shock attack unit, but dont expect them to survive combat with cc specialist units.