They are extremely effective for what there intended purpose is, to penetrate armor units. ROF is a legit gripe, but if you take time with them you can run them back and forth between your line and the enemies and really get some value out of thier assults.

That being said, they arent very good at anything else, save for chasing down fleeing foot units. So yeah, effective unit if used for thier stated purpose but not very multifaceted if you ask me, and for that reason thier value/effectiveness as a unit is somewhat limited.