I'm just now building up an Airborne Carpe Diem. I wouldn't worry about the frame. They have a very nice guarantee. I have a friend who's wife is on the Air Force Racing team. They use Airborne.
Do a google search. You'll find few if any owner negatives. I did extensive searches to see what was out there before I bought a frame set. However, I only investigated two frames: the Valkyrie and the Carpe Diem.
Litespeed is a more sophisticated frame, they make more high-end frames/bikes and you pay a lot more for them. Litespeed Ti frames are 4 to 6 ounces lighter than Airbornes's in general.
The main reason I went Airborne is nobody makes a frame like a Carpe Diem, it was only a few hundred more than the equivalent steel frame and it seemed to be the best Ti value. It wasn't a cheapie, $1400 for the frameset.
Titanium is stronger than steel or Aluminum, generally the frames are lighter than steel, about the same as Aluminum and heavier than carbon. It doesn't corrode so most are not painted, just polished. It's hard to work and to weld. It has a much longer life than Aluminum or Carbon. Supposedly Ti frames absorb road vibration better than Aluminum or steel but doesn't feel as "dead" as Carbon.
Airborne's are made in China. Supposedly a welder has to be trained for two years before he's allowed to make a frameset. Litespeed's are made just a few miles NE of Chattanooga. They give factory tours if you call ahead.
They supposedly have a dealer network, but it would have cost me another $150 to go through the lbs. They don't seem to support their dealers all that well as they compete with them with their WEB sales.
Al