Read the Bombing Guide on the wiki. It's pretty good.

Agreed Rss is better

Thats like asking if cautery blade is worth getting.

Radiant Sun Shards. Ionized Salt Bomb is like a cruel joke by the devs. Although I would wait a bit on crafting either- they say they've got new weapons in the works.

The poor ISB. I feel so bad for it. It wants to be the most awesome bomb in the game, but it fails so hard.

Being Normal/Piercing it does great damage against Wolvers. DBB is still better though since with Wolvers you are usually dealing with many and they are tightly packed; whereas Crystal-line bombs really work better on single targets. Might work with Trojans, but the RSS is the bomb with the Fiend bonus. And Trojans are frequently accompanied by Zombies, which calls for an RSS too.

The shock proc is very frequent, and the shock damage is as strong as the VT. But shock is most effective on Undead/Construct. If up against either of them you are better off using RSS, making the lure of shock moot. And shocking a Wolver is like tickling their underbelly. The shock might interrupt an Alpha, but it isn't worth the effort.

The slime bonus is a joke, literally. Salt... slime... haha. The employees of OOO are quite the jokesters. I know it is silly, but I really do appreciate their efforts.

Regardless of all the above, I'd still pull out the ISB for fun if not for the charge time. Oh, that charge time. At MAX CTR it is slower than a Level 1 Nitronome with no CTR at all. I would spend all my time charging, running, dodging... where the damage comes in, I don't know. It takes forever. The party might clear the entire room before you get 2 of these things on the floor. Bombs are very situational, and by the time the bomb is ready the situation likely dissipated.

So yes... such potential burdened by contradictions, destined to simply collect dust.

I'll put it simply:

RSS for the standard damage bomb every bomber simply needs as it supplies much elemental damage that most bombers sorta lack unless they are Lockdown junkies.

ISB for a hipster weapon, though a weak one at that. At least it doesn't slow your movement speed though... like *gulp* BAB or Irontech. Only way to even attempt a decent use of ISB is with CTR max. Otherwise its a bit trolly.