My sample has arrived
I'm sat at work so I can't provide pics of it, but I'll post some later.
The top surface is very detailed, this particular sample looking like lava between rocks (it's from the
Despoiled Reaches mat. The lava effect is very good, with lots of tiny holes on the areas that represent the crust. The rock areas are fairly flat with small crack details, and overall the surface is flat enough that models won't fall over (although my Chaos Raptors might end up proving me wrong there), but textured enought that a drybrush will bring up all the little details and look really effective.
It rolls up very tightly, so even the largest mat shouldn't take up much room - certainly a lot less than the
GW grass mat sheet I have does as it needs to be rolled up fairly loosely. It's also tough - I've given the sample a few good pulls in various directions and it hasn't split yet, and it's pulled back to it's original shape, so for general use it shouldn't get damaged. I wouldn't recommend putting anything sharp near it though, unless you're intending to cut it.
The back of the sample, however, is very rough (think heavily textured paint like Artex), and as you put models on it they might fall over if they're a bit top heavy due to the way this rough backing affects the top surface when weight is put on it. It's also quite strange to see your fingerprints clearly on it where it's a pale colour, it's almost as if the latex reacts to oils in the skin. The top surface doesn't do this as noticeably, and with a light coat of paint shouldn't do it at all.
I've dropped a note to the manufacturers to ask if the final mats also have similar backing - as the samples are cut from a larger sheet I'm guessing that the actual mats are going to be like this, which might make them a little less useable.
On the whole the mat sample is very good, and a full mat should be a great playing surface.