well, like i said, it was a goofy idea i had when i was half asleep to begin with, so i guess there's really no way to make it serious. that said, i am more concerned with the mechanical balance than the fluff.

is this more or less powerful than other at will methods of flight available to PCs?

at very low levels, certainly. an orc with 2 flaws can pick this up at 1st level, while the game is designed for flight being unavailable until 5th level. i guess that could be addressed with a BAB prerequisite.

at very high levels, you can get higher speeds out of this than you can with fly or most magic items, but you are also more vulnerable than you would be with those other methods, as has been pointed out.

so, fluff aside, what should we do with this feat?

require you to end your turn on a solid surface or fall?

require you to spend attacks to maintain height? say, you drop 10 ft. per round at the beginning of your turn.

limit the number of consecutive rounds you can maintain flight? say 1+Con bonus, and then you have to rest for a minute before you can fly again.

note that i'm not wanting to turn this into either "your flight is so slow you can't actually do anything in combat", nor do i want "you can fly, but you can't do anything while flying or you fall". both of those are bad. you already can't charge, run, or dive with this feat, which limits your combat options enough, imo.