Customer Rating: 
Summary: Use WITHOUT Battery Grip
Comment: You can use this strap without having the battery grip attached by purchasing the Opteka hand grip since it includes a plate that screws to the bottom with a slot to thread the cord. This is what I have done as I prefer the Canon strap to the Opteka strap. Currently the Opteka strap on Amazon is only about $8, well worth it in my opinion to use this awesome strap instead when you don't need the battery grip.
Customer Rating:
Summary: Does the Job
Comment: Comfortable. Does the job. Takes away that concern you might loose your grip.
As many others have already said, however, I wish the thing came with instructions.
Customer Rating:
Summary: Can't Live Without It!
Comment: I'm on my second Canon DSLR(a Rebel XT and now a 40D). Both Have had wrist grips, on my Rebel I used a knock of Kata Model. On my new 40 I opted to go with the E1. Once it was on I immediately noticed the difference in comfort, the canon version has a little more cushioning which really makes a difference after a full day of shooting.
This wrist strap is maybe the most important accessory second or equal to the battery grip. Once your dealing with a heavy camera and a lot of glass it's impossible to put a long lens on and still use the neckstrap, its too much weight on that part of your body.
The only downsides I found were this version unlike the cheaper one didn't come with a tripod mount, so if your not using the grip there is no where to put the strap if I recall!
I would highly highly recommend this and for anyone looking to get into the hobby more seriously it is a must have.
Customer Rating:
Summary: Canon EOS Hand Grip
Comment: I like this hand strap on my EOS30D. Can't keep the neck strap on the camera, but I didn't like the neck strap anyway- always got in the way. I can carry the camera around with the hand strap for an hour or so. And if my hand gets tired, I just put the camera back in the gadget bag and carry that on my shoulder. The aux battery pack is required to use this hand strap.
Customer Rating:
Summary: Strap REQUIRES battery grip
Comment: Although not an inherent problem with the strap itself, the description does not indicate that a battery grip is REQUIRED to install.
Summary: Use WITHOUT Battery Grip
Comment: You can use this strap without having the battery grip attached by purchasing the Opteka hand grip since it includes a plate that screws to the bottom with a slot to thread the cord. This is what I have done as I prefer the Canon strap to the Opteka strap. Currently the Opteka strap on Amazon is only about $8, well worth it in my opinion to use this awesome strap instead when you don't need the battery grip.
Customer Rating:
Summary: Does the Job
Comment: Comfortable. Does the job. Takes away that concern you might loose your grip.
As many others have already said, however, I wish the thing came with instructions.
Customer Rating:
Summary: Can't Live Without It!
Comment: I'm on my second Canon DSLR(a Rebel XT and now a 40D). Both Have had wrist grips, on my Rebel I used a knock of Kata Model. On my new 40 I opted to go with the E1. Once it was on I immediately noticed the difference in comfort, the canon version has a little more cushioning which really makes a difference after a full day of shooting.
This wrist strap is maybe the most important accessory second or equal to the battery grip. Once your dealing with a heavy camera and a lot of glass it's impossible to put a long lens on and still use the neckstrap, its too much weight on that part of your body.
The only downsides I found were this version unlike the cheaper one didn't come with a tripod mount, so if your not using the grip there is no where to put the strap if I recall!
I would highly highly recommend this and for anyone looking to get into the hobby more seriously it is a must have.
Customer Rating:
Summary: Canon EOS Hand Grip
Comment: I like this hand strap on my EOS30D. Can't keep the neck strap on the camera, but I didn't like the neck strap anyway- always got in the way. I can carry the camera around with the hand strap for an hour or so. And if my hand gets tired, I just put the camera back in the gadget bag and carry that on my shoulder. The aux battery pack is required to use this hand strap.
Customer Rating:
Summary: Strap REQUIRES battery grip
Comment: Although not an inherent problem with the strap itself, the description does not indicate that a battery grip is REQUIRED to install.