Had mine Revo'd, I would estmate 0 to 60 time down by about a second, maybe. The real difference is in the torque. There is a massive difference in overtaking, the power difference is unbelieveable. Was considering getting mine AMD'd, but went for the Revo after the 5 hour trial. AMD physically change the chip, Revo is done through the serial port by the bonnet pull, they don't even lift the bonnet. If you have you car re-mapped or chipped, it's like watching TV, once you've seen colour, you don't want to go back to black and white. Do it and you will never regret it.
As far as fuel consumption is concerned, if you use the performance of a chipped car, then you will pay the price at the pumps. Drive it hard and you will only get around 20 mpg. Drive it like a pussy cat and you'll get 36 mpg easily. If mpg is important get a TDI, don't chip it and do 30 mph everywhere.