I work in the heavy equipment world as a repair technician. They are doing some pretty cool things with LPG now that is really bringing the power back up to regular gas engine specs. Direct propane injection has been developed for quite a few forklifts and they perform quite well compared to a gas powered unit. The old carb style mixer body systems that convert the liquid to a vapor to be burned are the ones that are notorious for being wimpy and quite sensitive to temperature changes.
Its definitely here to stay, but not as cost effective to convert vehicles to over on this side of the pond.