I have had no problems with my ipad2 battery since I got it until I charged it last night on my new Apple docking station. I found no change when I upgraded to OS5 last week until this recent charge.
Usually I use the power plug that came with it or my car charger. My battery generally lasts a very long time. Today I started with 100% charge. I did not use it at all until I turned it on about 11 am and the battery was down to 50%. That seemed odd but I did a few emails and then closed it down. An hour later with no use it was down to 38% where it stayed for 3 hours. I now have it plugged in on direct cord charger and will test to see how long this charge lasts.
I am thinking this has to be the fault of the docking station although it is an Apple ipad product. I used it with my regular power cord and it did charge.