Surprised not too many people here have posted about this... but then again, this has always been more of a picture forum rather than an equipment forum. Here's a link to the Sterlingtek equivalent. I've got 6 of them and all work wonderfully.. and longer than the Canon branded batteries. Oh yeah... good warranty and they will back it up.
http://www.sterlingtek.com/twocabp18bap.html
I forgot... if you put together a $60 order, the shipping is free. I got a spare charger and a couple of batteries for both mine and my wife's pointandshoot. Worth the free shipping....
Forgot to include...I use them right next to Canon branded batteries in my grips on my 30d (with the bg-e2) and 40d(with the bg-e2n). The grip manages them down independently anyway. Heck... you can swap a single fully charged battery into the grip and leave a partially charged battery in it and it performs just fine.
Just my 2 pennies...