Grand Scale -- EXCELLENT
I regularly lurk at alt.food.barbecue, the home of the barbecue purists. Believe me, thease people are hard-core. I've seen them rip apart someone who happens to call grilling barbecuing. Here's their definition of barbecue from their FAQ ( http://www.bbq-porch.org/faq.asp
There are many interpretations of the term 'barbecue' in the world. Some people use it to describe a social gathering and cooking outdoors. Others use it to describe grilling food. For our purpose here, we are using the term to describe meat, slow-cooked, using wood smoke to add flavor. There is equipment designed just for this type of cooking.
Barbecuing is not grilling. Grilling is cooking over direct heat, usually a hot fire for a short time. Barbecuing is cooking by using indirect heat or low-level direct radiant heat at lower temperatures and longer cooking times. The distinction between barbecuing and grilling is the heat level and the intensity of the radiant heat. It is the smoke from the burning wood that gives barbecue its unique and delicious flavor.
THere's nothing in there about heat source. The relevent phrases are: "slow-cooked", "wood smoke to add flavor", "lower temperatures", and "longer cooking times."
Here's another definition from their FAQ:
A somewhat-derogatory term used by wood-burning smoker traditionalists referring to those who choose to barbecue by using gas or electricity to fuel their pits and wood chips and or chunks for smoke. The Lazy-Q'ers thereby relieve themselves of the necessity to expend any but the most trivial effort in the act of barbecuing
So even they admit that gas or electricity is an acceptable way to cook barbecue.
As far as there being a difference in taste between barbecue preoperly cooked over gas and cooked over wood or charcoal, I can't tell the difference, and I doubt any of you can in a blind tasting. In fact, many of the teams at barbecue competitions (yes, there are such things,) now use gas to fuel their pits.
So, if your gas grill can hold the temperature at 220 - 250, and you have enough gas and wood chunks, you can produce not just acceptable, but outstanding barbecue.