I've not used my wheel once yet - what's it for???

Oh, you're going to love this.

Okay, play a playlist. Press the red button a couple of times until you reach the "Now Playing" screen, which is essentially the same thing as the Now and Next screen on the Empeg, the list of songs that are currently playing.

Okay, now roll the wheel up and down to reach a song, then push in on the wheel (it has a button just like a mouse wheel does). You'll get a menu that lets you re-order and edit the current song running order. With wheel pushes and rolls, you can fiddle around and re-order songs, moving them up and down in the list, deleting, adding, etc.

Then, if you want, you can use this screen to save it as an actual playlist.

That's just one of the cool things you can do with the wheel, there's others.