In reply to ian.richard:
I think they're great, but I couldn't justify the cost at the time we bought our family tent, when air beam ones were still fairly new and very expensive. We don't go that often, as my wife's not a huge fan of camping.
I'd definitely consider one now, though - couple of friends have them and rave about them.
Was once chatting with the chap in my local Millets - he said they kept a spare "pole" in store for every tent they sold, but they'd never actually sold one, which is encouraging.
The down side, as others have said, is the packed size and weight - although that might just be a function of the size of tent they make possible.