I've been playing around with the Zuzzy samples: mainly cutting them to 20x40mm rectangles to flock my bases.
(I've gotten annoyed with sand/gravel because it tends to gum up the magnetic sheeting that holds bases down in my travel cases)
Zuzzy stuff looks good, and one of them they advertise as 6mm as well -- it's a lava-flow land, so pretty fractal.
Haven't pulled the trigger on a big mat, or a big mat for base-making yet: it's a bit difficult to cut out 1/4" inch circles to seat Epic miniatures (if a paper hole punch worked easily, it'd be ideal for this purpose. I'm also unsure of my ability to scissors cut it accurately for basing.
In terms of the larger mats, I am curious how well it works with 'hills' placed underneath.  It seems this may be one place where the latex sheets and felt work better than printed plastic or paper mats.
On the other hand, the other thought I have had was using Worldworks games printed paper, both as modular gameboards and matching bases. ÂÂ
Still trying to decide... ÂÂ
Of course then there's also covering the sand and gravel in Gesso-- seems to do a pretty good job of cementing it to the base.
Another interesting and tempting one is:
http://www.saboldesigns.net/combatmat.html