Well, don't know how good or not this is depending on how you see it.
But currently CEX will give you a trade value of £21 for your Sixaxis controller.
They Sell their DualShock 3's for £30, So by trading in your Sixaxis you can get a dualshock 3 for £9.
Now I took advantage of this yesterday because I remembered having a neglected Sixaxis stored away in a cupboard as it has had a lot of abuse before this day. I can't remember which game it was but the sixaxis has been flung across the room a few times in frustration. However it still worked but I bought a new one a few months back.
Anyway, if, like me you have an aged Sixaxis that still works (cause cex tests them) you may want to take advantage of this offer.
What's more they let me choose which DS3 I wanted, as you know they are second hand, so I chose the one that was in better condition than the others.
AND YOU GET A 12 MONTH WARRANTY!