If you're going purely by description, it seems like marking the sizes of rooms & passages on the map would be far more useful than gridlines. Grids mean you have to stop and count squares, even when the whole map lines up nicely. If there are blueprint/layout-style numbers indicating that the corridor is 8 ft wide, then that's the simplest thing in the world to figure out.
If I weren't using a battlemat, and every building was still in sizes evenly divisible by 5, with walls that took up no space, I would *really* have to battle the urge to crack jokes.
To answer Merric's earlier question, I'll either (a) describe the sizes, but not very precisely. If the room's 85 feet by 25 feet, I might say "It's gotta be nearly a hundred feet long, and about a quarter that wide". If the PCs want to bust out the surveying & measuring gear to get precise measurements, they can do it, and I'll count the squares (or if they use magic -- there's a rod in one of the Books of Eldritch Might...). If a fight breaks out, I'll sketch out the shape of the room, so players can get a feel for things.
Option (b) is that I just draw the map on the battlemat (erasing old parts for new parts, as needed). Then, I do occasionally feel the pain of weirdly shaped and sized rooms. But I just draw an approximation for the fight -- I'm not terribly worried about it matching the map precisely. Even if it lines up perfectly on a grid, I'm going to screw up drawing it.
(When the players mock my inability to draw a straight line with a ruler, I add HD to the monsters, increase their numbers, or both. Well, I always consider it, at least; I can't remember if I ever actually have done it.

)
When we first started 3e, the group liked to map things out; afterwords, I'd give 'em a photocopy of the map (assuming they explored everywhere), and let them compare. We haven't done the mapping thing in a while; it may be because someone asked, "Which of the PCs is actually wandering around with paper and pen in hand, and not a weapon, anyways?". Of course, it's also been a while since they've been on a big dungeon crawl. THe recent "location-based adventures" have had smaller or more modular locations, and have thus been easy to either keep in mind, keep on the battlemat, or sketch roughly on the whiteboard.
(When I say "sketch roughly", the emphasis is on the
roughly. Draw well, I do not. Can't emphasize that enough.

)