Gas engines do have several advantages that make them very inviting to fly. In fact, because of the cost of fuel I am working to get more gas engines in my hanger and get rid of some of the glow power. But there are a few down sides that need to be considered when thinking about gas engines.
1. They are for larger models. As said above, 60 size is the smallest gasser out there right now. And even that won't fit all 60 size planes.
2. RFI. Gas engines can and do develop radio frequency interference (RFI). This can cause problems with your radio, so steps need to be taken to ensure that they don't interfere.
3. Vibration. Gassers tend to vibrate more than glow engines. Once again, not a huge problems but steps do need to be taken to keep them from causing airframe failure.
4. Fuel safety. Gasoline is a lot more volatile than glow fuel is. Safety steps need to be take in the storage, transportation, and handling of gasoline. At the very least you should purchase a fire extinguisher to keep in your vehicle and for use on the flight line. You also need to store gasoline away from any open flames or sparks. Glow fuel can't be ignited by a spark, but gasoline can and will explode if ignited by a spark.

Just giving you some things to think about. Moving to gassers can have a lot of advantages. As I said above, I'm starting to work towards getting more gassers in my hanger. Even though the price of gas has skyrocketed lately, even at $3/gallon it's still cheaper than glow fuel!!

Good luck

Ken