Firstly, I think that last year's draft was an extremely poor one in terms of "skill position" players, hence the early selection of so many linemen.
I'd also say that Joeckel, Fisher and Johnson (I had them evaluated in that order) weren't great prospects. In fact, I had all three of Warmack, Warford and Cooper higher than either Fisher or Johnson.
I'd put Lewan behind only Joeckel of last year's trio. He has athleticism but requires more refinement. Personally, I wouldn't draft him on his sketchy personal background (which has been well documented both on these forums and elsewhere) alone. However, he has the ability to be a solid, if unspectacular, starting left tackle.
Matthews is the highest rated of the trio in my mind and should make a consistent "Pro Bowl" standard left tackle throughout his career.
Robinson, as you say, has great potential. However, I am often sceptical about potential over substance; I've seen far too many over-hyped prospects fail to deliver in all three of the sports that I follow closely to be easily convinced by rave reports without solid foundation. That's not to say that Robinson cannot become a great left tackle; I just don't see any cold, hard, evidence at the moment.
I'd draft Matthews (ideally after a trade down to six or so), then Robinson. I wouldn't touch Lewan for the reasons mentioned earlier.
