This grip is a very useful add-on to the 5D mkII. The main benefit, for me, is that it provides another set of buttons to use when shooting in vertical format so that you can hold the camera more comfortably. In addition it provides more battery options, i.e. ability to load two batteries or to use AA cells (in emergencies perhaps). The grip is very well made, and attaches to the camera solidy despite using just the one screw to do so. The only issue I'd raise is that it is quite wide and fairly square in profile, so people with smaller hands might not find it the most comfortable thing to hold.