I have had a number of iPods, starting with a 15G 3rd generation. I added a 2G Nano 1st Gen for use when walking, with the Nike kit. I added a 512MB Shuffle 2nd Gen for use when I mow the lawn, shovel the driveway etc.
When I got my iPhone, I stopped using all of the others...
The shuffles are great though for loading pretty much a single playlist, and for taking them somewhere that you might not like to take your "main" ipod, like to beach, etc.