Not a Hall-of-Famer but he was actually a very productive player from 2004-2010, despite the strikeouts. During that time, he hit 231 doubles and walked 750 times, so he did more than just hit home runs (of which he hit 242 during that seven-year stretch). For that period, you had a guy who averaged 33 doubles, 35 home runs, 107 walks, and an OBP of .371 per year, which is typically somebody you want on your team. Keep that up for a few more years and you've got a bona fide Hall-of-Famer, regardless of the low batting average and poor fielding.
He aged quickly, though, and his production really fell off when he moved to the AL and into the designated hitter spot (which may have had something to do with it- some studies have found that players hit worse as DHs than as everyday fielders, but Dunn was not a good fielder so there would be a trade-off).
Sabermetricians tend to find him a fascinating player because more than almost any other player, his at-bats resulted in one the "three true outcomes," a home run, a walk, or a strikeout. See
http://www.beyondtheboxscore.com/201...omes-milestone
A lot of people found him boring to watch for the same reason.