There are lots of good things to see, but there are question marks as well. Hageman was said to be capable of wowing coaches and scouts at the Senior Bowl, but reports are he wasn't outstanding in practice or in the game. He had a chance to be a Combine workout warrior, but his drills were decent, not great.
The Steelers are putting their homework in on Hageman anyway, which is smart. He has as much upside as any player in the draft, given his size and the displays of athleticism he's shown in his career at Minnesota. A team that can get him to go hard every down is getting a potentially dominant player (he'd likely be a 5-technique defensive end in Pittsburgh). He was, at one point, a possible top 15 pick, but he's dropped in the eyes of many to later in the first round, maybe the second.
He's a tough add at 15 for the Steelers, but due diligence on one of the draft's biggest enigmas is critical.