The Kamvas 20 is a really good product, I recommend buying it especially if are a mid level professional illustrator or graphic designer. Is a really good product on a budget.
I have this model since June and one of my friends tried and wanted to buy a graphic tablet, so I recommended him this one. He is really happy with it and told me it was a good recommendation. About the product, I should say that, in my opinion, the size of the screen is ideal, and is a very good tablet to jump into the digital art world. Due to the material of the screen you can feel the screen roughness a bit when you paint, which is not necessarly something bad, as you paint on a layer above the one where the image is shown (difference between Kamvas and Kamvas pro, apart from the buttons). The pen has got a good pressure level range and is good and comfortable. It includes the stand, which is necessary, ans is really useful. I also use this screen as a second screen.