Summary: I keep the BG-E4 on my 5D all the time; it has never been removed since I received it from B&H. I love the battery life and the vertical controls as I never find myself contorting my arms to frame a shot. I do wish that the BG-E4 were able to sense the on/off status of the 5D instead of having a second on/off switch just to enable the vertical buttons. When I have a 580 EX II attached, I find myself turning 3 switches to 'on' before I take a picture (flash, 5D, BG-E4).
Summary: I love the feel of the grip. It counters the weight of my L series lens nicely and having the extra shutter release and wheel is awesome. Plus the extra battery life is great for those long award ceremonies.
Summary: I use the product for sports, weddings, and portraits. In general the grip feels great in your hands and balances out some of the heavier lens like the 70-200. Having the additional shutter button when you switch to vertical shooting is incredible and helps save your hands and fingers from cramping. I suggest this for all 5D owners.
Pros: Durable, Good Value, High Quality, Shutter button, Vertical shooting
Summary: I say that the battery grip is a great add-on to the camera. It holds even better to shoot whatever your kind of work you do. A camera like the Canon 5D feels a lot much better with the Battery Grip, I assure that.
Summary: I use this sturdy battery grip EVERY TIME I use my camera. It allows me to shoot longer periods of time and makes me feel like my camera could shoot for an eternity before the batteries give out(This is a wonderful feeling when you know you are going to be shooting for hours at a time). The grip also gives the camera a more balanced feel; with the extra weight at the bottom, it feels more natural to hold in your hand... and it looks darn good too.
Pros: Charges Quickly, Comfortable, Easy To Install, Good Value, Lightweight, Long-Lasting, Reliable, Tuff-sturdy
Summary: I already knew I was going to buy this when I bought the 5D. I have been using a battery grip on my other body for a couple years and love it. Now with the 5D with a 24-70mm and the 70-200mm lenses the 5D didn't balance well at all. I needed to rush order just to feel comfortable in my hands. With the grip the 5D feels very well balaned even with smaller primes. The grip is also very useful when shooting portrait position.
Pros: Balances the Camera, Good Value, Long-Lasting, Reliable
Summary: The shutter release button on mine does not work properly with the grip turned "on". I can't press the shutter half-way to activate metering and check focal point, etc. It just takes the photo, with either shutter release, the one on the grip AND the one on the camera(that's right it messes up the shutter release on the camera as well when the grip is turned on).