A while back, in the comments, Max and I got into a colloquy about how to drink while in "aero" on a tri-bike, without falling off. Max suggested the new Profile Design system that rests a traditional (or aero) water bottle on the aero bars, where they are easily accessible. I bought it. I hated it. My aerobars are set fairly close together, and with the water bottle and apparatus resting on top, the bottle interfered with a variety of my favorite hand positions. Also, when I hit a pothole, the bottle tried to jump out and nearly caused me to crash. I removed it after two rides.
Right before the NYC Tri, I decided to spend another chunk of change on the design that everybody else seemed to be using . . . This was also a Profile Design system, but instead of sitting up on the bars, the bottle rides between the bars. This seemed to work much better. The attachment to the bike was much firmer, and the bottle rested lower, so I did not feel like the straw was going to poke out an eye if I hit a bump. The only problem is that the lid seems to be designed so that you can refill on the fly by pouring liquid from the frame mounted bottle or a bottle exchange quickly without opening the container. I find this leads to a certain amount of splashing while the container is full. After a few sips, though the problem goes away. I've been using water, so it's no big deal anyway. I think Gatorade or other high tech nutritional drink might be more of a problem.