My 5th Gen iPod Video with 15k tracks is very sluggish.
When album art is turned on, the device is very slow. Playing an album will cause a 10+ second delay before the music starts while it's looking up the art. Sometimes, if it can't find the art fast enough, the iPod will skip to the next song. This is actually really bad on anything that's bookmarked (like audiobooks or movies) because it loses the position of the bookmark. Even if the music manages to start playing, the iPod "locks up" for many seconds as it does a go-ahead lookup in the cache for the rest of the album art of the stuff I'm playing.
When album art is turned off, everything plays immediately without any delays. There is no lockup, either.
I have to believe a better caching system would fix this, and that is should be fixable with a firmware update. I returned one iPod already doing this (the guy at the Apple store said it shouldn't behave this way). When the 2nd iPod did it, I figured it was an institutional problem. I'm hoping a future firmware update on the iPod will help.
I tried this solution to no avail.
Update: Well, it's not clear whether it was the pave that did it, or the fact that I have the iPod using the Macintosh disk format instead of the Windows format, but it seems to be happier this morning with album art. There is a delay of a couple of seconds after picking new music, and no more locking up. Yay! :)
Now playing: Don't Speak - No Doubt