I love the idea of the millimeter scanner but find the progressive scan to be almost a headache! And occasionally it'll scan a bush and the bush will look like a crouching enemy!? Plus, you very rarely spot an enemy because the enemy has to be completely still!? I would rather have something like 4 to 6 scans operated by myself, and rather see enemies even if they're moving. Just thoughts anyways!
I've never found it useful, though the recoil seems to be better when I do use it Probably just my imagination..
The MMS is a very situational piece of equipment. If you're using it by trying to scan through everything, then you're limiting yourself and your play style. Think of it primarily as a type of Red Dot Sight that has a little added bonus: the ability to see through walls. So, play normally, then use it to scan into rooms or corners before you proceed. For fast-paced games like Dom and KC, it probably doesn't have a lot of uses. However, I do find it a bit useful in HC Dom for scanning flags and other areas. The low health means you can punch through walls pretty effectively with it in HC Dom.