I have one from here
http://powerklick.co.uk/landrover.html
and it rocks as yet 10,000 or so km's on it and I wish i did this a long time ago. Things to think of when doing anything that increases performance, regular maintanance, good parts and oils and if you hear any noise under the bonet look or have it looked at straight away. (All of these things anyone should do anyway but I can't strees it enough once performance is incresased).
Install one of the chips and enjoy the drive.
Adam