I'm a Phillies fan. In regards to the "good guy" thing: he's a fan favorite who has always treated fans well. He's extremely competitive and plays hard (e.g. plate collisions), but I don't think he's ever crossed the line into dirty play.
I'd put him in the Hall of Fame, but I'm obviously pretty biased. I will say that, aside from Roy Halladay and Cliff Lee, I think Utley (when healthy) has clearly been the best player on the Phillies since his first full season in 2005.
Utley grades out pretty well by JAWS, a sabrmetric system that takes into account both overall productivity and a player's peak production. As has been pointed out, Utley definitely suffers from a lack of longevity compared to other HOFers. Utley's problem (compared to other HOFers) isn't just that he's been injury-plagued, but also that he didn't become a full-time regular until the relatively late age of 25.
http://www.baseball-reference.com/leaders/jaws_2B.shtmlOn a tangent, when GW Bush (who used to be a Texans owner) was asked who he would pick to start a team from the ground-up in 2008, he chose Utley and Roy Halladay.