I like to use the flip-mats, but I also use gaming paper for large complex maps I want to have pre-drawn. The gaming paper comes in 30" x 12' rolls for a reasonable price, and has a 1 inch-square grid printed on it.
The real advantage for gaming paper is that I can sit and draw out large numbers of maps, have them prepared, but even so can still bring them along because they are lightweight and fold easily.
I think I might pick up some gaming paper when I'm up at Leisure Games this August. My thinking is that I could use it to pre-draw areas for published adventures, especially for areas that are complex and/or are likely to see repeated use.
I'll have to consider price vs utility though, and the question arises: If I am going to take the time to pre-draw maps on paper, could I not pre-stick dungeon tiles to cardboard & get something prettier, if less accurate?