I figure when you think Semin, you should think (right after the obvious jokes) people like Vanek, and that guy that married Carol Alt. He's somewhere between a perimeter scorer and a KHL risk.
He could be a 40 goal scorer on an Ovechkin and Backstrom line (which would signal desperation by the Capitals, and therefore not sustainable), or a slap-happy fighter (he will NEVER live that down) on a lesser line.
I've owned him, and been frustrated. If you decide to own him, it'll be a season-long commitment: you won't be able to bench him, and you'll rue the weeks he's active. But occasionally he'll explode for mega-points. Are you that patient an owner?
Let your competitor own him for a while. Then lowball HIM.