When ol' Blue came to live at my house, she came complete with a set of aerobars. As this thread (aerobars and bellies) seems to fit me perfectly, as I have both, I feel like I should respond!

As pointed out, the aerobars give me an additional position to ride in, so I stay more comfortable for longer distances. And, when working into a headwind, I pick up an extra 1.5 mph without having to work any harder! I don't ride down on the bars all the time, but I do try to work on increasing the time I can comfortably stay on them. And, my thighs hitting my belly remind me to pass on that extra helping at the next meal, too!

What do the pros do? Don't have a clue! But, my Coach, a collegiate athelete, rides on the aerobars for an entire 20k race! Of course, competitors like him are always searching for the Holy Grail of the Aerodynamic Flat Back, while I do it just for a little extra edge in comfort, distance or speed.

"Ride what works for you" seems to be pretty good advice, at least it has worked for me!