Mike Mearls ponders about the benefits of having a grid. Interestingly, he doesn't like the "grid as arbiter." Most interestingly, he asks for a poll. Coupled with the disappearance of minis, might this mean that something gridless is on the horizon? (or at least, they are thinking about it.)
It's interesting that 3.0 falls in the "DM as judge" camp, whereas 3.5/4e fall in the "grid as judge." One more reason for me to like 3.0
When I played 3.x, we used a grid for a while, but eventually dropped it because we felt it wasn't worth the effort (we just didn't use the rules in a way that required it). When I ran 4e I used one, because I felt like I had to - all those position- and movement-based rules! I did go without it once, but it was for a single combat that pitted the PCs against a single monster so there wasn't much tactical movement going on.
Archaeology is nothing like Indiana Jones. I've never once gotten to punch a Nazi!
A man may do both. For not we but those who come after will make the legends of our time. The green earth, say you? That is a mighty matter of legend, though you tread it under the light of day! —J.R.R. Tolkien
I'm not used to using an acutal grid. My usual game style involves me looking at a GM map and giving vague information, then if the situation gets critical I'll sketch a quick map on a piece of notebook paper and use dice/etc as minis.
I've played 4E both with and without a grid and I find that without plays faster for my group.
Marv / Finarvyn DCC playtester (2011) C&C playtester (2003) I'm partly responsible for the S&W WhiteBox Builder of the TrollBridge Master of Mutants; MA since 1976 OD&D Player since 1975
"Don't ask me what you need to hit. Just roll the die and I will let you know!" - Dave Arneson
I've been doing more reading in Playing at the World, and find myself becoming re-intrigued with 4e in particular as a really good example of the mode-switch inherent in all editions of DnD, from Exploration as free-form to Combat as a more-or-less defined tactical-level wargame.
Looking at it that way, if I played 4e, I'd definitely use the grid, and be explicit about the switch. My brother has been playing 4e for awhile with his kids and wife, and they use a grid without any issues. I think it actually helps the kids...