If they face OKC, I think the Mavs won't have too much trouble. If, on the other hand, they face the Grizz, I think it will be interesting. As LakersFan pointed out, the Mavs rely a great deal on outside shooting; the Grizzlies have very good perimeter defense.
I'm also curious to see how a matchup between Dirk and Z-Bo would go.
Still, I think the Mavs are a really, really good team and they are definitely playing better than anybody else in the post-season right now.