Aero bars aren't necessarily uncomfortable. I've heard enough users of aero bars say they're comfortable for an alternate position on long rides, including the state time trial championship which includes some marathon distances that would be impossible for me to do in an aero tuck.
Even with an old neck injury (C1 and C2) with chronic pain and stiffness, I could get reasonably not-too-uncomfortable on the Profile Carbon Stryke bars, and stay in an aero tuck up to 5 minutes. In contrast the old school Scott bars were torture and I couldn't stay tucked for more than a minute at a time.
If we're not limited by current UCI rules (which are just stupid, but that's UCI), the best aero bar position is probably the "praying mantis" position, which angled the forearms upward so the hands were in front of the face. Most users say this was both comfortable and more aerodynamic because the hands serve as air foils for the larger head. I've used that position on both my old Scott and newer Profile bars and it was effective, good for a 1 mph boost even with my limited abilities.
Not to start a ruckus over old PED scandals, but I'm going to use Floyd Landis as an example. Floyd was an unusually effective time trialist, something that's been forgotten amid the scandals. He was an odd looking fellow but his relatively massive lower back and hips, compared with the rest of his physique, made him a formidable cyclist under any circumstances. It was somewhat reminiscent of Merckx, who also had a massive lower back and hips, on top of an already fairly large physique for a cyclist.
Here's a photo of Landis as a teammate of Armstrong, from 2002 (before mandatory helmets). Note the time trial setups -- pretty close to current UCI regs. Forearms nearly parallel with the ground. Floyd's bullhorns are lower. Lance stuck with his preferred position, more stretched out, no drastic drops between saddle and bar height. The bikes weren't the highly specialized TT/tri bikes that dominate the scene now, so it's closer to a hybrid road/TT setup we'd use for non-competition rides.
Floyd Landis following Lance Armstrong, 2002 time trial. Note the differences in aero and bullhorn bars and overall bike fit.
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And here's a photo that's more representative of the time trial position Landis preferred in his post-Armstrong support role. Landis used the then-UCI legal praying mantis position.
Floyd Landis TT bike setup, 2006. Praying mantis position. More effective use of hands to divert wind around the larger face/head. No longer legal for UCI competition.
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Skip to the 6:30 mark of this video (the link may already do that) and compare Floyd's TT bike position with his rivals. He was consistently more aero and looked more comfortable in the tuck, particularly compared with Oscar Pereiro who was eventually declared the 2006 TdF winner after Landis was DQ'd.