my wife an i both have (had) iphone 3gs. my update was a disaster. somehow the update created a 24 GB mystery file (the same size as the data on my phone). then it tried to load all my data and the mystery/shadow file. i was not surprised when it failed to get all 48 GB on my 32 GB phone. i will leave out the analogies that i am dying to include. i had to backup and restore the phone. that worked surprisingly well. i didn't lose any data. i just had to wait an hour while it transferred 24 GB at sub USB 1 speeds.
the wife's phone didnt go smoothly but it went better than mine.
all-in-all i would say iOS 5 was worth it. i like the free texting between iphones and the pull down menu.
then 4 days later i got the iphone 4s so i could talk dirty to siri. i think she likes it. for those that wonder it took about a third the time to load songs and apps on the new phone.
i7-930, GA-X58A-UD3R, Crucial MX100 512GB, 2 TB WD Black *2 mirror, ATI 5850 1 GB, 12GB (3*4GB)
Nikon D600, Tamron 24-70 & 70-200 2.4 VC, Nikon 50 1.4, 85 1.8, Sigma 35 1.4