It is expensive, but also, useful for some applications. Battery life is Ok. Did a couple of time lapse for 10 minutes at 5 seconds interval. Worked there well.
For macro shots, it really helps with remote focus using an iPAD to you select your focus point, though you have to use live view. Then, the camera battery live suffers. This is where an AC adaptor for camera comes in. I looked at Canon ACK-E6AC Adapter Kit for Canon 5D and am considering acquiring it. May be, for me, in July.
Hope you'll like it.