I've got one and I bloody love it! They map up to around 100bhp, sometimes more depending on the map.
I've not seen amazing MPG on mine though.. As it's a 45 litre tank, I've worked this out as meaning whatever I get from one full tank, I divide it by 10 to get a rough MPG.. And the most I've had out of a tank is about 520. That was taking it quite easy too!
They handle well if you have them set up right too. Interiors are bloody lovely too and have a very sporty look for such a cheap car!
Avoid the SDI like the plague.