It is fantastic for us in the UK - I have a petrol station in my home town, one halfway to work, and one about 400yds from work - so I never need petrol anymore! And with a gallon of petrol being close to ten dollars now, and gas being less than half that - it is brilliant! I've yet to finish a full tank of LPG since I fitted the new front end gas kit (the one mine came with was badly bodged in, household lamp cord and bare wires everywhere) - but when I do run out, it'll automatically switch to petrol, beep at me to tell me it's done so, and I can work out the equivalent MPG as I reset the odometer to zero when I filled it up.
Exdecuk - does your conversion have the "emergency" feature of being able to start on gas? Basically you hold down the changeover button before you even start the engine, it takes a few cranks, then fires up - I normally do this all the time to do without petrol altogether. Seems not a lot of people know about it, including my LPG installer mate in Wales - but he tried it the other night at 0 degrees, and it worked - on a Prins system. Mine is AEB/King. Try starting it with the change button held in, then hold it at about 2000rpm for about 30 seconds - can be a bit hesitant at first, but I have mine down to a fine art! Still keep a full tank of petrol and a 25 litre jerry can of petrol in the boot, mind!