Hiya!
I don't quite understand why so many folks are "against" flight at low levels.
Actually, scratch that. I have a theory...
Many of the DM's who poo-poo flight ability at low level are likely the type of DM's who like their "Adventure Paths & Stories" to unfold as they expect them to. I'd also say that many of the DM's who have no problem with it are the type of DM's who like the story to unfold as the Players dictate. (basically, "new school" versus "olde skool", I guess).
For me...a decidedly "Olde Skool" DM... I present the world as I see it in my minds eye. The Players react to that as they see fit. So, in my game, a sextet of adventurers find themselves at an impasse; a HUGE river, 2 km wide, probably with huge crocodiles in it (or worse!).
Now, a "new school" DM might be expecting the PC's to build a raft out of the wood from the collapsing ruins of an old log cabin, make their way across, get attacked by the giant (and hungry) snapping turtle that lives in the water (and is why the cabin is deserted...it's owners having been eaten years ago). BUT...if the PC's have a means of flying everyone over the river...well...then this "cool and climactic battle" that the DM was looking forward to and ties into a Druid NPC they can meet on the other side...is decidedly FUBAR. Ergo, the DM feels "cheated" that they didn't get to run the encounter, didn't get to hurt the PC's (and thus have them be in debt to a Druid's help), and the hour and a half he spent "designing the encounter" is wasted. So... "Flight is bad!"
On the other hand, an "olde skool" DM presented with the same scenario wouldn't have the same reaction. Sure, there might be disappointment that the "cool water fight with the turtle" didn't go down, but the general mindset isn't of "presenting a story" so much as it is "letting a story present itself". The OSDM wouldn't be expecting the PC's to do anything specific other than "get to the other side" (and even that is up for grabs!). So if the PC's fly across, decide to walk downstream or upstream, or even just turn around and say "Nope. Not crossing that river"... that's all fine. The challenge is "here's a river" in the OSDM's mind...in the NSDM's mind it's more "here is an encounter in a river".
I hope this is making sense. Basically, "expectations of play". "Specific storyline oriented DM's" might be more prone to annoyance with Flight-capable PC's because it messes with the "narrative the DM want's to tell", I guess is what I'm trying to say. I, as an older style DM, don't care what the PC's do or the choices the Players make...whatever they do, THAT is the story being told. That's one of the main reasons I love DM'ing...I never know what the PC's will do or what turn the story will take!
^_^
Paul L. Ming