Coburn doesn't get as much press b/c he doesn't have anyhting in his gaem that really jumps out at you. The guy takes care of business in hid own zone very effectively but not very spectacularly. He's pretty good offensively but its not like he has teh big booming shot or is great at rushing the puck.
IMO Coburn is just a really realiable 2-way defenseman that can be one of those players who can give you 25+mins a night. The guy is solid in all aspects of the game IMO and is becomeimg more physical as he gets older it seems.
I think there just 3 different kinds of defenseman who really excell at what their individual strengths are.