I can only hope folks do their homework before buying one. CNG engines have issues like any other and it's key to understand what some of them are. CNG is mostly methane gas, about 70-80% methane. It burns about twice as hot as gasoline so internal temps will be higher. Because of the heat generated, you need to use an oil that is at least 1% or less ash. Most dual rated diesel oils are in this category or there are special CNG motor oils available. Failure to use these oils can result in glow ignition and the owner may not be able to turn the engine off. CNG engines produce LOTS of water vapor. The exhaust system must be designed for drainage and of rust resistant parts or it won't last long. There have always been issues with cold start up in extreme environments with CNG. The fuel does not want to ignite at temps near zero. Then you have issues with fast fills at cold temps. The issue is not with the vehicle but with the dryer that is in the compressor that delivers the gas. Ice crystals can form and it restricts the fuel from entering the vehicle tank. It can take hours to get a tank full. CNG, while a higher octane rated fuel, produces less combustion energy and fuel mileages are about half that of gasoline and pretty much mirror ethanol in fuel mileage. Depending on the engines, if they bump the compression ratio to at least 10:1 they might get a little better fuel mileage but as a bifuel vehicle, expect issues when running gasoline. The issue is with the unstable gasoline we have today. Then you have the tank capacity has to be near double to get the same distance between fillups as a gasoline engine. The extra weight is probably not going to effect a truck but it may limit the beds useful area. Then you have availability which is getting better but there are some areas you can't drive off into and make it to the next fillup.
There are pluses and most of those are known so I didn't bother with listing any. Until they've worked some of the issues out, I'd avoid them for now. While farmers have been using this fuel for decades and have no issues with it, a soccer mom or a stock broker probably shouldn't even consider one.
