How effective are unsieged tanks?

I've noticed that siege tanks outside of siege mode are much more effective than they were in SC1 (in which they were almost useless). Anyone have any insights on how powerful tanks are, or are they still just there for the siege?

 

They do fairly well they're just not as cost effective outside Siege Mode.

 

the only thing that bothers me about that unit is the armor

 

Actually, while I haven't tested it myself, I've heard many times that they do more damage in tank mode against single, armoured targets than they do in siege mode. So if you want to take down a Thor or Colossus, unsieged is the way to go (as the splash damage doesn't go past the radius of those huge units).

Against smaller armoured targets, like Roaches, Stalkers, and Marauders (where the splash would amplify the tank's damage massively) I think it more depends on how many there are, and how mobile you need to be.

 

Mobility and what you are fighting are definitely important. Sieged tanks won't help you if stalkers blink on top of them, or melee gets into your marine ranks (killing marines with your own splash damage).