jmucchiello said:
I'd be curious to see how some of the posters on this thread would characterize the various styles of play that D&D somehow forces onto the players. It is a basic assumption of this thread which, IMHO, is not as universally felt as the posters may think. Different posters will list different break points and focus on different effects of those levels as being the "turning point". Some of the obvious turning points are fly, teleport, raise dead, commune, etc. But how these things change play will not be universal.
Let me preface what follows by saying that 3.X is my favorite version of D&D ever and I would NOT be playing D&D right now if 3.0 had not come out.
That said, I've seen several times when suddenly (and without warning because I wasn't paying close enough attention to what was on the horizon) the tenor of my games was radically changed by a new ability obtained by a PC. One session, things were progressing as I thought they would and the next things were VERY different and I had to alter the way that I was running the game (and other PC's in the party had to alter their role in the group) to accomodate this new feature.
A couple of early and simple ones might be Fly (as you cite) but also Levitate and Fireball. Suddenly those ranks in Climb that the Ranger had been cultivating for several levels are far less useful or critical than they had been up to that point. Fireball is a biggy because a massed group of enemies is now going to be considerably weakened before they make contact with the party unless they figure out a way to approach the group undetected or with excellent cover. In many cases, there is no reason for them to suspect that the PC's will have such magic available. In addition, the Fighter types in the group, who have been expected to "take the battle to the enemy" as soon as possible in order to catch them flat footed or give the Magic User types room to maneuver, are asked to Delay in order to let the "big bang" magic take effect first. Again, I'm not sure that I'd call these huge changes in play style but they are different than levels 1-4.
I was running my first game that went into level 10 and beyond when I got broadsided by Teleport. I should have seen it coming but I didn't. Suddenly the Wizard in the party says, "There are some supplies we need and some information that we should convey, so let's head back to town!" *Poof!*. The party had been way off in the wilderness and struggling to survive in hostile territory. Now they were seriously considering "adventuring by day and spending evenings at home by the hearth".

This campaign had a very fun and satisfying finish wherein I managed to accomodate and even require Teleport as part of their strategy but it took a major shift in my thinking to do it.
The campaign I'm running right now had a similar instance. The PC's are moving through hostile Drow jungles (Xen'Drik of Eberron) and must infiltrate one of their cities. I'd planned a couple of sessions at least of them stealthily dodging patrols, setting ambushes and that sort of thing before they could sneak inside the city. Suddenly the Psion in the group says, "This new power of mine lets me shapechange into a Pegasus. I'll just fly us in using Invisibility." I was just as happy since this campaign is running just a bit longer than I'd intended but that was a bolt from the blue. Suddenly the creeping pace of overland travel is once again circumvented and the PC's have unprecedented mobility.
I'm not angry or disappointed about these sorts of changes but they do happen. I most enjoy the "early levels" from 1-7 and it is because I feel I can more accurately predict what the PC's options are in that range. I've got no interest in railroading them and happily rolled with the punches when the PC's pulled the aforementioned tricks out of their bag. But I'm a better GM when I'm a prepared GM and I want to give them the best time I can. So I like it when I have a better idea of what is coming.
For what it's worth, the next two games slated to be run in our group are Black Company (which has a much more low magic system) and Warhammer FRP (also more low magic). I'll be a player in both games and I think they'll suit me fine.