I have one and they are great fun. can be a be in your face when giving the car some beans but good fun. my wife wasnt happy i was getting one but has grown to love it.
Here's a vid if mine http://youtu.be/C9Skz82Q0Fk
Also another of a chaps from Total Mini I think. http://youtu.be/qZIJsQYOofc
Can't comment on how easy they are to fit as I had mine done whilst the car went in for other work but its only supposed to be 20 min job.
I got mine for quite cheap on eBay, alternatively they always pop up for sale on total mini. Sent from my iPhone using AutoGuide.com App