Zhydaris, one of the official StarCraft 2 Community Managers, has answered a few questions regarding the Baneling's functionality, interactivity and a slight look into it's psychology.
1. Last we heard, Banelings have a detonate command that causes them to instantly explode and deal damage no matter where they are on the map. The command is available even while the Banelings are burrowed. When using the detonate command, do Banelings have to unburrow before they detonate, or do they detonate underground and deal damage just the same?
The Banelings cannot detonate while burrowed, they have to unburrow first and then explode. I know what you’re thinking. “Hey, probably exploding while burrowed would be a better warfare tactic”. You must understand that exploding in the name of the Zerg is indeed a great satisfaction for a Baneling, thus they prefer to unburrow in order to showcase their enthusiasm for their role by exploding with a smirk on their face. If you zoom close enough you will see a little smile on their little glowing face of theirs. Ah, gotta love the Banelings.
2. While burrowed, will a Baneling explode the moment a unit passes nearby, or will it wait for your command?
They’ll wait for your command. If you don’t tell them to explode, they’ll just wait while staying burrowed. That’s nice for setting up ambushes.
3. If you tell a Baneling to Hold Position, will it explode if an enemy passes too close, or will it wait for your command?
They always wait for your command.
4. In SC1, telling Infested Terrans to attack-move caused them to go to the exact location you clicked and then explode at that exact location. To simulate a normal attack-move, you had to tell them to Patrol. Will Banelings behave the same way, or will they attack-move like everything else — moving until coming upon the first thing it can target?
They’ll not behave like Infested Terrans. The attack-move command is not going to be interpreted as “Go and explode at this location”, but rather as “Move to this location and attack any enemy unit. If you can’t spot an enemy unit, just sit there”.
5. What is the power/range of the Baneling's attack relative to the Reaper's D8 Charge and the Raven's Hunter-Seeker Missile
It’s comparable to a D8 Charge, yes, the explosion covers pretty much the same area.
Battle.net - Regarding Banelings