Vertical power grips are common accessories for DSLRs these days. Heck, even your local department store carries some designed to fit many popular cameras. It's not surprising either. These accessories offer several big advantages for the photographer. They tend to improve the ergonomics of the camera for many shooters, plus make it easier to shoot off frames with the camera oriented vertically. They also provide an extra battery to power the camera, meaning fewer stops to change batteries. Some vertical grips even come with accessory adapters to accept AA batteries in an emergency.
Generally, camera enthusiasts have a choice between the camera maker's offering and three or four different generic models. The general consensus is that the camera maker's version offers better manufacturing quality and will work better with the camera it's designed for than the generics, but of course, costs a bit more. Other than that, there's usually not a big difference since even the generics usually provide a vertical shutter and the same control buttons the camera maker's grip provides.
One company, Satechi, does offer a battery grip that provides more options than other vertical grips. The company's LCD Timer Vertical Battery Grip includes an LCD display (which can light up) interval function, date and time display, stopwatch, multiple frame function and single frame long exposure function. It's also priced competitively at $119.95.
