It appears that in the latest software update for my 40GB iPod photo, Apple took a lot of the "thinking" out of the iPod's hands.
For example....
A lot of my listening is based on smart playlists. I'm particularly fond of using a "Haven't Heard In A While" playlist, which corals everything above a certain rating which I haven't heard in the last two months, and randomly plays it. When you're not wanting to actively hear a particular song, it's a great way to listen.
Prior to the latest update to the iPod, if I listened to 10 songs on the playlist (let's say of 800) on my iPod, then restarted the playlist, it would correctly report that I have 790 songs on the playlist... the other 10 having been removed from the list, because their "Last Played" bits had been reset by the iPod.
Today, if I listen to 10 songs out of 800, then restart the playlist, I'm back at 800. In order to get it to recognize the change in the number of songs on the playlist, I have to sync the iPod up with iTunes, which, as you noted, updates any songs I've added to the iPod and any songs I've *PLAYED*. It never did this before. Note that this includes songs that I played on the iPod, being synced back onto the iPod with updated information. No idea why it has to do this, since the "last played" bits are obviously set somewhere on the iPod, since it's able to give this information back to iTunes, which then updates the songs and passes the information back to the iPod, which now correctly reports 790 songs.
I don't know WHY Apple chose to do this, but unless there's some compelling reason that I can't figure out, I wish they'd un-do it. It's made Smart Playlists a lot less useful for the way I listen to my music, and I can't see what benefit I'm getting in exchange.
It was particularly annoying on my recently completed three-week roadtrip, where I didn't have my iMac, and therefore my iTunes Library with me. It means that any time the iPod playlist was reset (syncing photos from my camera, leaving it too long so it shut down, etc.), my playlist reset. Not a big deal that I have to listen to the same song over again, or skip past it... but annoying that it's not updating when it could be, and it used to be. It also meant that my playlist didn't get updated with NEW songs which should have been on the list by the third week of the trip, because it was stuck with what iTunes had told it last time it synced, instead of figuring things out for itself, like it seemingly used to do.