Agree totally it is down to paying the price for a competent installer - we did a V8 XC90, and after the installer realised he should have put a bypass in to stop the fuel pump trying (and failing) to pump petrol in as well as gas... well, he apologised profusely, free first service, and whole shebang was sweet as a nut after that. Honestly did not see much drop in power, but would kick over to petrol when flooring it in outside lane at - errr - "70 mph".
I would be interested in any recent experience of Jeeps with LPG; thinking of one for towing horsebox, as well as 20-mile return journey to work. I know the servicing costs are high, but am more concerned about all the horror stories about burnt-out valves etc (I only put about 20K on the Volvo before I sold it).