The unichips have their good points - mainly the number of tuners around and that they are generic so you can probably install it in other cars with a retune.
However they are technically not a good way to tune a car. When you use a unichip, you dont change the ecu's tune - you just change what the ecu thinks is happening so the ecu does something closer to what you want it to do. If its not done right, the ecu can tell something funny is going on and it can learn around the unichip (lots of unichip customers have posted this). As a result, everytime you reset the ecu you get a big boost in power which then slowly returns to normal.
Unichips are also bloody expensive for what they are. It doesnt cost much more to get a full aftermarket ecu such as an EMS stinger installed that you or any dyno shop can tune. Or you could go for an chiptorque (which retunes the ecu) and an off the shelf tune and get 95% of the performance gains at half the price.
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Stoke me a clipper, I'll be back for Christmas