Yes, the warp core breaches delivering a massive explosion. The bigger the ship, the bigger the explosion. You have several seconds to get out of the way, and I suggest you do so – especially if you shields are down at the time.
GrandPotato, eddie: Will there be boarding parties? If so, can you capture vessels, or does that just disable them or something?
Yes there are boarding parties. It's a Bridge Officer skill that launches shuttles at a target. The more crew you have (bigger ships have bigger crew), the more shuttles you launch. The shuttles can be shot down, and if that happens, you will lose those crewmen. If they make it to the target, the boarding party may damage and disable the ship's crew, and systems. They will then transport back to your ship (so don't blow up the target ship when your boarding party is on board). There is also a security team skill that can be use to repel boarding parties.
Descender: Will STO have a tactical feel similar to the old Starfleet Command games, where you could utilize almost everything on your ship, from ECMs to Tractor Beams? Or is it more focused on movement and shield management?
Space combat is entirely tactical. You will manage power, shields, position, firing arcs, engines, Bridge Officers as well as your own abilities. There are hundreds of player and Bridge Officer abilities from Tractor Beams, boarding parties, ejecting warp plasma, cloaking devices, emergency power, sensor scans, sensor jamming, deflector beams, attack patters, holograms, ramming speed, and on and on and on.
Mikx: How many bridge officer abilities do we have available in space combat (abilities per npc) and can we change them on the fly?
Well, you will start with one Bridge Officer with one ability and can eventually have up to 12 abilities active at one time on high end ships – about 5 or 6 seated Bridge Officers or various ranks. You can eventually have around 8 or 10 (still TBD) Bridge Officers total in your roster – each with 1-4 abilities each. You cannot change your bridge officers in combat, but you can change them any time between combat.
Phillip: How much of a destroyed ship will be available to loot?
Destroyed ships drop loot similar to other RPG or MMO games. Some will drop nothing, while others might drop rare items.
Mikx: In an interview, a developer stated that science vessels now innately target subsystems. Is that still the case, and how does that work?
Science vessels have the innate ability to target an enemies subsystems – weapons, shields, engines or auxiliary. When you activate this ability, your beam weapons will weaken, or "debuff", that subsystem. There is also a chance the attack will take that system offline for a short while. Some Bridge Officers also have a skill to target subsystem. These skills are better than the innate versions available to all science vessels, but they are limited to targeting a specific subsystem. So any ship can target subsystems if they have a Bridge Officer that has the skill, but you will need to dedicate 4 Bridge Officer skill slots to have access to all 4.