Probably few. But they don't need to. I'm starting to see people with their new iPads, and what they find to do with it. It really doesn't matter if Galaxy or Xoom can match or even beat it, people are finding the iPad to offer a solid product that does more than they imagined in a form that is extremely convenient. And then their friends notice. Snowball. Hill.
Most people wouldn't even consider one of the other tablets even if it was equal to or better than the iPad. The iPad is obviously a very solid product and it offers the most for the dollar. The only way another tablet will move at all is if it is half the price of the iPad. IMHO, it's the Apple brand that makes it so. People strongly identify with the company and have complete faith in their products to the point that the only way they will consider an alternative is if it is really cheap.
Look at the car market, even the luxury car market. You can choose from Mercedes, Lexus, Infinity, BMW, etc. All our great products and have models at similar price points. All of these brands are doing well. In the tablet market, it's only Apple.