I know the experts don't recommend it these days but I still use lava rocks in my old gas BBQ to get a better flavour. I also have a Weber charcoal one but sometimes it is just quicker / easier to use the gas one
When it is time to change, those hybrid gas/charcoal ones look very good.
My mate who lives in the US has one and was saying what good value they were. When I showed him how much they cost to buy in the UK he couldn't believe it - at the time we were being charged double the US pay for them. Not sure they have got much cheaper in the last 18 months or so.