Not sure if this is a "hint" or a known feature, but I've found it very, very useful however. I want to use my Shuffle primarily to play music, and occasionally to transfer files (i.e. as a USB disk). I don't want to have to manually unmount the Shuffle each time I pull it out (which you have to do when enabled for disk use), nor do I want to continually have to check "Enable disk use" when I want to transfer files. But it's easy to get the best of both worlds:

1. Uncheck "Open iTunes when this iPod is attached" for your Shuffle.
2. Uncheck "Enable disk use" is also unchecked.

Now:

• If iTunes is open and you insert your Shuffle, it is available and will auto-update and auto-dismount as required. Pop it in, update, pop it out. Easy.
• If iTunes is not open and you insert your Shuffle, it will mount as a disk. Drag files using the Finder, then eject the disk when you're done. iTunes doesn't get involved. Also easy.

[robg adds: I tested this with my Shuffle, and it seemed to work just fine. Strange that it works as a disk when disk mode isn't enabled, but it does so just fine. One cautionary note -- a friend with a Shuffle tried this, and when he re-launched iTunes after making the changes, the machine locked up tight. We're not sure how/if it was related, but it happened when I asked him to test this hint for me -- sorry Kirk!]