Update inbound!
@greatorder: It sounds like they have made repair costs much friendlier, yes. We'll see when the update hits, I guess.
re: building aircraft: I sympathise with your frustrations on getting aircraft to fly straight, having tried to build simple aircraft properly. There are suggestions over on the official forums to add a center of mass indicator to help players build aircraft which will at least fly straight. If devs ever add that, it would help immensely; otherwise, the next best thing you can consider is posting pictures of your aircraft here and hopefully someone can help you figure out how to make your aircraft work. (If I'm online and see a picture, I'll try and help whoever posts.)
re: flyer balance: There's a counterargument that aerofoil flyers suffer worse performance at lower tiers because of roboranking limits. Essentially, the parts required to make a low tier flyer restrict the amount of EHP and/or weaponry you can bring with you, compared to ground bots in the same tier, as they can use on tier or T-1 movement parts and put better guns on. As the roboranking limit increases, flyers get tankier and at T10 when everything caps out, plasma bombers suddenly become flying fortresses.
In short, the majority is of the opinion that flyers are OP, but only after you get past the initial steep curve of building a functional flyer.