I was curious about this too (and I'm guessing you've been playing a gungineer?). As far as I'm aware the score goes up towards 5 or so (maybe). I've had pretty low scores, and my highest was a 3.8. Right now I think it's more of an interesting number, but there's a lot of things I don't like about it.
Like I pointed out in my matchmaking thread, a rating system purely based on player actions isn't going to cut the mustard (kids still say that, right?). If you're a pilot of a disabling ship, letting your ally get all the kills, your score is going to be low. If you're an engineer and you're put in the role of gungineer, you won't be doing as much fixing/buffing; and your score will be really low, even if you're absolutely obliterating the other team with your gun. If you're a gunner and your pilot has a fear of facing the enemy, you're not going to be able to shoot them effectivelly; your score will be really low.
It's a very team oriented game that's a lot more complex than 'How many things did you fix', and therefore pretty difficult to make a good rating system.
Also (I haven't done any gunning with this system) there are some of the score criteria I don't like. As a pilot, one of the ways to get a better score is to kill opponents... with your ship. So if you don't ram kill them, your score will actually be a little lower. Then you have to shake spots as well? As a captain, I'm generally a little preoccupied with wanting to kill the enemy before they kill me, which reduces my ability to run away into a cloud to shake a spot. As an engineer, one of them is buffing components. Which is nice and all, but if you run around the ships fixing this and that, putting out fires and such, you'll get a really good score. But not as good as if you had buffed components.
Overall I kind of like seeing it, but it can be a little misleading.