Never looked back mate.
The key here is Quality tyres.
The difference in ride quality is minor, and is quickly forgotten. I suppose its like when you go from Standard Springs to Lowering Springs like H&Rs or Eibachs.
More and more cars are being sold straight from the Factory with 19's now. Tyres prices are dropping just like the 18's did.
You can bet in the next few years a lot more New cars will be rolling out on 20's.