I used to show about 30 GB under capacity under iOS 4 on my 32gb iPhone 4.
Just checked after the update as the phone couldnt fit my backup back on, and its reduced to 28gb....... I havent been able to put my photos back on, and now ive only got 54mb free for new photos
Wirelessly posted (Mozilla/5.0 (iPhone; CPU iPhone OS 5_0 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A334 Safari/7534.48.3)
I think think the previous capacity was somewhere around 29.06gb, and now it's at around 28.something gb.
Good thing my 64gb will be here soon.