Wet erase battlemat from Chessex all the time. Have a bunch of Dungeon Tiles and older, Games Workshop, card floorplans (without a squared grid on them) but its too much hassle to find the ones I want for the adventure and time consuming laying them out - the battlemat is so much handier and I can designate different terrain with different coloured white-board markers. I sometimes pluck a selection of appropriate tiles out though for maybe a specific 1 shot convention adventure, since a small handful of tiles is less cumbersome that a long rolled up vinyl mat.
I also have some Dwarven Forge sets - wish I had more, especially their Medieval Tavern stuff but, again, its time consuming to lay out and I find that it detracts from the urgency and tension in an exciting session - might occasionally lay out a "special" room where the BBEG is lurking, just for added effect (ideally before the players arrive).
I used to always use a battlemat sized sheet of that 'grass' (not sure what its called) thats used by model train enthusiasts, complete with bundles of 'model' moss and trees of various sizes and colours for outdoor encounters/adventures but I find that its not really workable in 4th Edition because range/AoE effects seem much more important these days. I used to just make a best guess re, for example, the area or range of a fireball but I'm somewhat reluctant to do it with 4th Ed with all the mention of squares and such, and the tactical nature of the whole thing.