Space Combat is Star Trek Online's killer feature. It's relatively novel, interesting, and fun.
Combat is quasi-2D. There is a Z-axis, but movement along it is restricted. It's 3D-enough that you can do cinemactic passes underneath or above an enemy ship, but the combat itself is effectively 2D. No Immelmanns for you.
Combat is not really frantic, it has a measured pace that works extremely well. Also, there are explosions, which always improves everything.
Your ship has four shields: fore, aft, left, and right. Weapons are all about firing arcs. The starter ship has forward phasers and photon torpedos, and aft phasers. Photon torpedos have a narrow firing arc, so you can only fire them when your target is directly ahead. They also have a longer cooldown. Phasers, on the other hand, have a very wide firing arc. If the enemy is to the side of you, you can fire both phaser banks at them.
So much of the early game is using phaser broadsides to weaken shields, trying to keep a strong shield between you and the enemy, and getting a photon torpedo to strike through a hole in the enemy shields.
(Tip: if you right-click your weapons, you can set them to auto-fire. I think you still have to fire them once before auto-fire kicks in.)
However, new weapons can completely change how you fight. On my first ship, I got a Disruptor Cannon, which did a lot of damage but had an extremely narrow firing arc, and a Disruptor Turret, which did low damage, but had a 360 degree firing arc. So now, if I faced the enemy straight on, I did a huge amount of damage because the Cannon, Turret, and Photon Torpedos were firing. However, as soon as I had to turn, damage dropped off greatly.
As well, if you keep one side facing the enemy always, that's the shields which are going to be pounded, so there's a nice tension where you have to keep rotating which weapons are firing and which shields are taking hits.
You can also adjust power for your various weapons. You can send more power to the shields, or the weapons as you need.
Long-term cooldowns are special abilities given by your bridge officers. For example, my Engineering officer can greatly boosts the shields every few minutes. (I envision "Scotty, I need more power to the shields!" "She cannae take much more of this, Cap'n!" when I click that button.) The Science officer does something with Tachyons which damages the enemy's shields. It's a very neat way of handling cooldowns, and very much works with the IP.
I am not very far in yet, so I don't know how the rest of the game will pan out. However, I think Star Trek Online is worth trying for the space combat alone.