This mix is interesting, because it's not even close to being OCRemix's shortest mix, but seems terribly short regardless. When you compare it to 'MindOfTheMotherBrain', another of AmIEvil's mixes which is just 6 seconds longer, you'll notice that the Metroid mix uses up its short time much more effectively and as a result feels about 75% longer than the mix at hand.
I don't think it is just because 'MindOfTheMotherBrain' is a better mix (although it is). It probably has more to do with the shape of the mix. 'AmIEvil' takes us from A to B pretty methodically in one perfectly drawn arc. My theory is that when we can see our destination, we get there faster, and that's the case with this mix. There just isn't enough substance to brake our pace.
Overall, an unsurprising and brief listen, but so is a lot of videogame music in general. It makes the grade.