As ussual, it's mostly a matter of balancing penalties you have to take seriously agains the advantages.
Were it me, I'd start the (angelic looking) race with 40' and poor maneuverablity. Huge penalty to Disguise as a normal humanoid. Minimum clearance of 20' while flying. Make taking off a full round action requiring at least space for a 30 ft movement in a straight line (like a charge). I'd create 2 of feats for increasing speed (with both Str and Dex prerequisites that get progressively higher), and two feats for manueverability (with tumble skill requirements). Finally, limit it to a number of hours per day equal to 4 + con modifier (so it doesn't become your default method of long distance traveling). Feat to improve that too (skilled Glider or something similar). This makes speed more appealing to fighter types, and agility more a light fighter/rogue shtick, and all day trecks a barbarian/ranger thing. You could eat up a lot of feats learning how to fly well...
So, How do I make a player really aware that he's a lighter-than-you'd-think creature? Lower that massive damage thresshold to 35 or so. Size is considered one category smaller against all bull rush, tripping, and grapple attacks. Increase the critical hit multipler of all bludgeoning weapons by x1 against this character (light bones, breakable wings). Limit flight to lightly encumbered. Remember the penalties to flying for less than 100% HP. Increase the cost of all armor to 150%. And for those spell casters who think they are so sly, add a concentration check as if casting defensively to any spell casting while flying (you have to remember to cast and flap, and you're probably airborne for defensive reasons anyway). Add a -4 penalty to spell casting defensively while flying.
If you're feeling genuinely cruel, then a -2 penalty to Reflex saves (big cross section, harder to make abrupt movements) and/or +1 damage per die from fire. I dont think their neccessary, but they are options. I would give serious though to the loss of speed/manuverability while wet though. Not everything with wings is a duck.
In otherwords, this is not the convienient sort of flying magic gives you. After that, I don't think you'll hve a problem fitting in 1-2 small flavor abilites and still calling it ECL +0.