Legion looks fantastic, lets get that out of the way. He's well detailed, his sniper rifle is great and the cables around his shoulders and head move freely when his head and arms move, which is pretty cool. I thought he was a fantastic twist in ME2 so was glad to hear he'd made it to the action figure series.
However, his articulation is terrible! His arms allow bending at the elbow, and his forearms can twist, which would be amazing, his shoulders allowed them to move forward further. His hands are also somewhat useless at holding his gun in most positions. As with most of the figures, I've resorted to putting a small piece of blu-tac on his hands to keep the gun in place, which I don't really mind, but better sculpts shouldn't be too much to ask for.
His legs are also completely crap, his left leg seems to be a couple of millimetres shorter, which means without his base, he might not stand too well, and there's basically no rotation in them anywhere.
Overall, he's a great sculpt visually, a terrible one mechanically. If you're happy with a fairly standard pose then he's not too bad.