Peter Gago, Penfolds is quoted as saying:
“Screwcaps scare me, they are not a problem for white wines but for Grange they are not a solution. I’m worried about the interface of metal and wine over time, “

here:

http://www.wine-spirit.com/articles/...categoryid=275

Screw caped wine for short term consumption at airports and inflight, why not. For long agers... not there yet.