There's been no esthetic revolution in the Nikon SLR line. The D200 resembles previous models, and is not really much bulkier than its entry-level cousins. The compactness that is a real plus - but it's a lot heavier! In fact it's the heaviest camera in its category. That heft comes from its professional construction, based on a complex cast magnesium alloy chassis. It stands up to heavy use without distorting, and should have no difficulty using professional lenses, which are themselves often very heavy. The body is obviously coated in plastic, with the quality finish that Nikon is known for, but it also has sealed body seams - it's not watertight, but it should be able to deal with getting caught in the rain, or use in high-humidity or dusty environments.
In many ways, the D200's construction and build quality bring it close to the level of professional models. As you'd expect, it can be fitted with an optional battery pack / vertical grip that lets you use a range of standard or rechargeable batteries. This grip also provides better ergonomics for certain types of intensive use, such as shooting in portrait mode; the tradeoff is the expense of extra bulkiness and weight. You should consider both the advantages and disadvantages of this accessory before deciding to purchase it.