I hadn't really used the batteries before this weekend, when I was photographing my sister's wedding. Playing it safe, I had the two fully charged sets of batteries as well as a 10 pack of Energizer alkalines, for use in my SB-800.
The performance of the Powerex was really surprising for me. I expected a set to last maybe until mid afternoon (shooting began at 9am). At the end of the night at 2am they were still going!!! The flash would take a bit longer to be ready after the last shot, but otherwise there was no difference from morning to late night shooting.
I was also surprised that with the Powerex, my flash would fire when taking a sequence of shots. With normal Energizers the flash would fire on the first shot and just not fire on the second shot when using the high speed mode on the D300.
In my usual shooting (sports/action) I don't use the flash at all so I have no experience to compare this to, but I was very surprised by the battery performance and give these a big thumbs up
