Neat article in the latest ESPN mag* about how/why Monta Ellis is working for the Mavericks. Basically the point was that the Mavs are uniquely structured to where you can insert a player like that and take advantage of the things he does do well without the problems taking too much away. A big factor being that Dirk drops back on pick and rolls, so teams have to stop Monta from driving (which he's pretty elite at) and also stop him from getting the ball back to Dirk or one of their other shooters. Plus that Calderon is a pretty good backcourt mate for him because he's so efficient and doesn't require the ball (really much of the team is like that), but can still "run" things without clashing in a way that derails the team.
*I got like three years for five bucks or something just for Insider ages ago plus one dollar re-ups, the magazine is usually pretty trash. And I'll never understand why they made it so large.