I haven't yet painted on the placemats, but have painted on other material, such as aprons from Zazzle. The aprons turned out great, so I imagine the placemats will work well too.
However, if you would like to wait, I ordered a placemat myself, and will post about my experience.
Note, that the placemats takes an extra 7 - 14 days to process, before they are shipped.
Update: The placemat arrived and looks great. The yellow was a bit lighter than pictured online, but is still plenty dark enough to show up for painting it in.
The placemat is two layers thick and the edges are hemmed under. The fabric feels substantial and sturdy, and washed up well in the laundry. However, it didn't lay as flat once laundered.