I think the Lakers should win this series in 6 games, but I think Dallas is an excellent and underrated team. I don't know how we are going to guard a "playoff-mode" Dirk (a lot of people should love the Nowitzki/Gasol match-up), and I know the Mav's will have a chip on their shoulder for being called out as perennial playoff chokers.
The biggest concerns besides Nowitzki for the Lakers won't necessarily be Jason Terry. Their X-factors are Marion and Stojakovic. Marion (who plays great defense on Kobe) has a runner that seems to go in 70% of the time, and Peja has been one of the best trade-deadline pickups in the league, with a deadly 3-point shot. I see them winning games by making a lot of three's; I also see them winning by baiting Kobe into taking contested and difficult jump shots (or to bait anyone else into taking jump shots, which is done by the Lakers out of cockiness and laziness), and getting quick rebounds/steals and producing transition points. Transition defense is a weakness for the Lakers, except when a more mobile Odom is in the game.
The only thing for the Mav's, though, is that I don't see their home court as a huge advantage. They have some good fans, but I just don't see that arena as a huge threat. Another weakness for them is their toughness. They are maybe even softer than the Lakers, if that is possible. I saw some rebounding issues yesterday against a small Portland team, so if they don't address that issue, they'll be in some trouble.