not good, Smartbombs have been left uncheked for ages, they are drastically behind everything in terms of damage. they are not as terrible as FoF missiles... but still, any medium gun platform will outperform disco battleships for a fraction the cost.

the only place to use them is WHs, as already mentioned, you need an alt to get a good warp in, you land the capital and you smartbomb the escalation wave as it spawns. and even then, 1400mm artys or Tach battleships would do far better, and wont have you die horribly should you get jumped.

on pvp they just plain suck, more so after the last drone changes that made medium smart-bombs pointless unless its to kill Ewar drones.