***UPDATED JUNE 19, 2012***

I'm really pleased with this product.  I bought it to use with the&nbsp;<a data-hook="product-link-linked" class="a-link-normal" href="/Canon-EOS-Rebel-T3i-18-MP-CMOS-APS-C-Sensor-DIGIC-4-Image-Processor-Full-HD-Movie-Mode-Digital-SLR-Camera-with-3-0-Inch-Clear-View-Vari-Angle-LCD-and-EF-S-18-55mm-f-3-5-5-6-IS-Lens/dp/B004J3V90Y/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Canon EOS Rebel T3i 18 MP CMOS APS-C Sensor DIGIC 4 Image Processor Full-HD Movie Mode Digital SLR Camera with 3.0-Inch Clear View Vari-Angle LCD and EF-S 18-55mm f/3.5-5.6 IS Lens</a>&nbsp;and just got the&nbsp;<a data-hook="product-link-linked" class="a-link-normal" href="/Canon-EOS-REBEL-T4i-18-0-MP-CMOS-Digital-Camera-with-3-inch-Touchscreen-and-Full-HD-Movie-Mode-Body-Only/dp/B00894YYP6/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Canon EOS REBEL T4i 18.0 MP CMOS Digital Camera with 3-inch Touchscreen and Full HD Movie Mode (Body Only)</a>.  I've used it with both camera bodies, and the Battery Grip works fine on both cameras.

Another thing I like is that the Battery Grip works great with both AA batteries as well as with camera-specific batteries

I purchased it because I wanted additional power, as well as additional ways to power my Canon T3i.  This product does both.  It accepts 2 of the types of batteries that are designed for the Canon (I'm using the one that came with my camera along with&nbsp;<a data-hook="product-link-linked" class="a-link-normal" href="/Photive-Original-LP-E8-Ultra-High-Capacity-Li-ion-Battery-For-Canon-T2i-and-T3i-Canon-LP-E8-Replacement/dp/B006Y0YZZ6/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Photive Original LP-E8 Ultra High Capacity Li-ion Battery For Canon T2i and T3i (Canon LP-E8 Replacement)</a>, as well as standard AA batteries (I'm using lithium<a data-hook="product-link-linked" class="a-link-normal" href="/Energizer-L91BP-8-Lithium-AA-Photo-Battery-8-Pack/dp/B0000DC4EL/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Energizer L91BP-8 Lithium AA Photo Battery (8-Pack)</a>).

One of the things I think is really cool about this product is that there is a little slot to keep the Canon battery hatch, which you have to remove to use this grip (or any grip).  Perhaps that hatch holder is standard on the Canon OEM grip, and this manufacturer is simply copying it, but the fact they did include shows their attention to detail.  Another benefit of a grip is that it adds a degree of protection to part of the camera.