I just ordered the S100 and I've read so many reviews saying an extra battery is essential but when going to order one I get confused should I go all out and get an original or would a normal cheap one do the same job.
One of the agreed weaknesses of the S100 is battery life. It uses a standard NB-5L type. Most of the ones listed on Amazon have reviews that indicate less real-life power compared to the original. I would love to have a backup or two, but need to find a cheaper source with at least the same power density and I need to avoid the scams.
I put in a pre-order on Amazon a couple months ago, but it seems as if it's in limbo.
I have had the S90 which I lost in a cab in San Francisco :( and purchased the S95 to replace. I may sell my S95 and get this, the S series have been a great line of cameras for when I do not want to lug my Nikon D7000 or D90 around.