In New Zealand we have raced foam tires at all levels for many years now in electric outdoors.
I have done some big rubber tire races overseas and I can honestly say that foam tires are faster, cheaper and last alot longer.
It is also so much easier as you only have a few compounds to realistically choose from, you don't have to worry about inserts etc.
I can see where Rick is coming from on carpet but outdoors it is a different story.
I run the tire from about 62mm down to about 57 or 58mm and then use them at our indoor racing. So I can sometimes get maybe 15-20 runs out of one set of tires, depending on the compound. (you must note that traction additives is not allowed at any level of competition here in New Zealand)
I honestly cannot understand why it is not done in more places around the world.