Is There a Tablet Market?

"There's an iPad market, and the iPad could be classified as a tablet, from a hardware-centric viewpoint. But the market for non-iPad tablets is about as big today as it was before the iPad, which isn't nothing, but it's close enough to nothing that Apple doesn't need to worry about it."

Marco Arment (founder of instapaper) makes a compelling argument that there really isn't any true competition to the iPad at this time.  Sure, there's the Samsung Galaxy Tab or possibly the Nook Color, but how many people unfamiliar with technology asked for one of those for christmas.  Of course, CES is a few days away, and we're sure to see lots of tablets appear there.  It took years for the market to adapt to the presence of the iPhone.  I suspect the same will happen with the tablet market.  What do you think?  Is there a tablet market, or just an iPad market?