I've been reading this thread with interest.
I think most of you thinking about trying the grass-only route are down south, so as long as you have good ground and the right type of sheep and the right attitude, I can't see why that wouldn't work for you.
I did just want to record, for the sake of others reading this thread now or in the future, that grass only won't always work depending on ground, climate and breeding. So if you're a way up North (like me) and/or have rough ground (like me) and/or have a type of sheep that is unlikely to fatten in one season on grass, then you'll need to either run them on through winter and/or cake them.
And the other ingredient in SteveHants' model, don't forget, is ruthless culling for animals that don't suit the system. For sheepkeepers who are likely to find it difficult to send young ewes away for no other reason than that she has needed treatment for her feet, or that she struggled to produce enough milk for her twin lambs, then Steve's system is probably not the one for you.