I updated my iPod to iOS4 yesterday and plugged it in this morning to listen to some podcasts. At first I got an error message on the stereo that said "Connection failed" I then looked at the iPod and saw the "This accessory was not made to work with iPod" error message. Great I thought. I listened to podcasts everyday, if this doesn't work I'm willing to go back to iPhone OS 3.1.3 or just switch to my Incredible and use the line-input the stereo also has.
All I did was unlock the iPod and it connected to the stereo with no problem, all the stereo controls continued to control the iPod just fine. However when I stopped to get gas I had to go through the same procedure. Not a big deal but annoying and something I hope Apple fixes in 4.0.1 or whatever.
Besides that I went from 10 screens of apps down to 3 with the use of folders.