Remember Billy Flynn, the hotshot celebrity lawyer played by Richard Gere in the film version of the musical Chicago? That's our man Tanner Bolt, the choice attorney of jerk husbands suspected of killing their wives. Despite Boney's description of him as "'a last-ditch guy […] the guy guilty people call in'" (35.28), he really knows how to give 'em the old razzle-dazzle.
Maybe it's because we've been inundated with so many portrayals of sleazy lawyers (like Billy Flynn), but Tanner's character is a welcome surprise compared to our expectations. Even Nick seems to feel this way: "I pre-hated Tanner Bolt so much that I expected his office to look like a Miami Vice set. But Bolt & Bolt was quite the opposite—it was dignified, lawyerly" (29.9). Tanner himself is even a pretty likeable guy—he's "a confident man, the best in his field, a man who liked his life" (29.43). Because of this, we're willing to overlook his spray-on tan.
Not only is Tanner competent, but he also seems to care about his clients more than the average high-powered attorney. Think about the scene where he flies to North Carthage after Nick tells him his theory about Amy trying to frame him. This could have given him reasonable motivation to dump Nick's case: most lawyers would probably give up rather than risk marring their perfect trial records. But instead Tanner not only believes Nick, but works out a plan to reveal the contents of the woodshed to the police rather than allow them to find it on their own.
While he definitely loves fame and wealth, Tanner has a reasonable amount of intellect and concern for his clients. So though we "pre-hate" him right along with Nick, it turns out this guy isn't half as bad as he seems like he'll be… kind of like his client.