I bought this battery, and, it seems that it does BETTER than double! I love it.
I do not mind the extra thickness, and weight.
I run out of normal battery a few times a week during one days' usage (in particular when I am doing a 7AM-midnight day).
Of course, as I am very busy, I cannot afford to experiment, and NOT charge every night. But, so far, I have yet to be below 50% after one days' use. Also, I went one whole day in US last week, then took a flight to Europe without charging, played with my BB on th plane a bit, and used it the entire day in Germany, and I still had barely below 50% left.
This battery is a thumbs up!