Apple and Microsoft Tablets: Hardware Keyboard or Software Keyboard?

Whether it's the Microsoft Courier or upcoming Apple Tablet that launches first, the point is clear: tablet are coming. The only question left is how you're going to interact with them.

From the concept shots and information leaks, both Microsoft and Apple's feature on-screen inputs for doing a lot of things, but they don't talk about text input. Is it going to be a virtual keyboard? Probably. But that doesn't preclude a USB port for a physical keyboard.

What would you use? Obviously, if you need to take this around town, on the train or in the car, you'd need to use the onscreen keyboard. But what about at home and at work? Which would you prefer to use? And why?