I agree with toronto_cheesehead, Michael Johnson won't probably start as an every-down type guy, but will develop in to that spot in a few years. First few years he can contribute as a pass rusher while Jenkins moves inside.
I think if we're gonna go DE, might as well take Michael Johnson. I'd rather get an OT if there's a good one avaivable though.
Edit: I don't want to post multiple times, so I'll just ask you dhazer, are those mocks included with people that haven't declared yet. Because if none of the good QB's declare (which is highly possible), Malcolm Jenkins could be taken first by the Lions.