I have one in my car, a significantly better option than a piggyback. I used to run an E-manage and a re-mapped standard ECU is better in many ways!
The car is setup on NME 256 cams, full exhaust system etc etc and easily passes emissions come MOT time, which was ALWAYS a pain on anything else.
IMO, the best alternative for plug and play option and significantly cheaper than going for a complete aftermarket ecu such as OMEX, DTA, Emerald etc.