Comments about Hähnel Hahnel Battery Grip with Infrared Remote, for the Canon 40D, 30D & 20D Digital SLR Cameras:

Its good for the whole duel grip part.
Whats not so hot is the remote wireless trigger.
It has to be directly line of site to work. If you think firing los with Canon flashes is a pain,you havn't seen anything till you see this..

DO NOT get it if you just need a duel grip, there are others Adorama sells for bout $60 or so,,just the grip, no fancy bells & whistles.

As far as the duel grip is concerned, it does that part excellent. And I will say this, if all you need the wireless to do is take self portraits/group shots were you are in front of the cam, then it will work,, just don't be off angle too far!! ;-/

It stays screwed on pretty good, even using a big ol 70-200mm , sometimes a bit roughly.. just check it when you go to make sure its still tight, and you'll be fine.

It will add size to your cam, duh! and will make reaching some controls difficult, so have them preset, or flip your cam round to do any changes,,less you have HUGE hands, I do, and I still flip it to change sets, not hard tho.