No direct knowledge mate but this does sound very much like a 'back in the day' word of mouth verging on urban legend.
You know how it goes......new technology, a few back alley installers slat it in an already semi knackered car - thus every problem thereforth gets blamed on the LPG. Grandad tells your dad, who tells his mate in the pub, who tells his mate at work, who tells his kid, who tells you at break time.
Personally I'd give it a crack if its been installed by a reputable company...........only real pain is the lack of filling stations but if its dual fuel (petrol and LPG?) you might not be so bad.