I don't know if this is "help" but I recently replaced the run-flats with Yokohamas and am very happy with the new ride feel. As far as a spare, mine is a can of fix-a-flat. You can also get a portable inflator fairly cheap. I have never had a tire go completely flat immediately. If I had a nail, I could always get to the station. I know that the fix-a-flat may ruin the tire pressure monitor, but I really don't care. That is a pain of a feature anyway becasue you need to go to the dealer to have it reset any time it is triggered.
Velocity