Of course, raiding at level 60 is one way to use it, but you can go even lower than that -- want to farm Runecloth without it getting too boring? Roll up a death knight, and leave him in Felwood to grind on Furbolgs. Really love running, really running, Scarlet Monastery with your friends? You can all roll characters to 39 (or lower, if you're looking for a regular challenge), turn XP off, and leave them camped outside the instance. Turning XP off means you can create characters for almost any purpose, and having heirloom items (especially if you buy cloth, which any alt can wear, even if it means they take an armor hit in some cases) means that leveling them up doesn't take more than a few days of free time. Lots of interesting ideas to play around with there for sure.