The Zipp VukaShift aerobar extensions are awesome. Simply put, they integrate shifters and extensions in a way not previously possible. But to really get into why they're so great, we need to first understand the problem they attempt to solve.
Aerobar extensions are too often nothing more than an afterthought. Or worse, aren't involved in a rider's thought process at all. Joey Triathlete walks into the bike shop (or more likely, logs on to an online shop), buys the aerobars he thinks are the coolest, and just takes whatever extensions come stock on the bar. Who's to say that those extensions even work well ergonomically on the bar they come with? Who's to say they'll work well for Joey?
Extensions are necessarily one part of the whole front-end construct, which for a triathlete, is all about three things: the location of the pads, the location of the shifters, and the shape of the extension between them. Most of the time, those three elements work totally independently of one another: the pads are bolted on to something, the extensions are bolted on to something, and the shifters are bolted onto something that bolts onto the extensions. These disparate elements may or may not collude to provide a good ergonomic experience for the rider. And just because an aerobar comes stock as a complete system does not mean it's ergonomically good. But what IS good?
The general consensus is that shifters should ideally be located close to the same horizontal plane as the top of the arm pads. Some prefer the shifters slightly lower, others slightly higher. We prefer them to be just slightly higher than the pads, by a cm or two. Ideally, the extensions will slope up slightly before they meet your hands, putting a bit of a curve in your hand. Some riders prefer to have a little more of the slope in their hands, others less slope.
This was part of the design impetus for the first S-bend extensions. By using a curve, rather than a sharp bend, riders could select the amount of slope they wanted in-hand by grabbing a different part of the extension. Furthermore, moving fore and aft a bit during your ride didn't mean you had to get stretched out or bunched up -- simply change your grip on the S-bend, and you'd still be relatively comfortable. With a sharp J-bend, any fore-aft movement pretty much requires a compromise in either hand position or body position. But the advantage given by the S-bend had its own compromise, namely that the shifters can't be in your hand unless you liked having NO curve in your hand. This is because the shift boss required the extension be flat for 4cm or so to accommodate the plug. So the shifters would be out of reach if you like having any curve in your hand. But having shifters in-hand is vastly superior to having to reach out to grab them. Reaching out makes shifting slower, compromises your position, and requires more effort. An ideal extension lets you have a little extension slope in your hand AND still hold on to the shifters.
There are a couple types of extensions that do this well. Felt's F-Bends do this, but require you to have about an inch of pad stack to line everything up. Traditional J-bends to it well enough, if you like having an extreme amount of slope on your hands, and don't care about being able to move fore and aft much. Riders who enjoy the ergonomic benefits of S-bends have never had a good solution to holding the shifters. Until Zipp came out with the VukaShift extensions. Read on to see how Zipp tackled this problem.