I have to make little alterations to a lot of published dungeon maps to get them to fit on this mat. It always seems like a I need 5-10 more squares in one direction or the other. But this won't be a problem if you're making your own dungeons to fit this size.
Folding up is great for storage but the rigidness of the mat makes it not want to lay flat once it's unfolded which makes it a hassle to keep your figures in the right spot/upright. I usually have to dedicate some time to laying books over it to get it to lay flat for the upcoming session.