I have had 2 fail on my Q220 as well. I did manage to get one of them covered by Weber. A fellow I work with had one fail too.
They gave me all sorts of "tips" via email as well such as using only the 1 lb bottles or if a larger tank is to be used to only use the Weber adapter hose. The Weber adapter hose failed in about 2 years too so I'm back to using a cheaper hose and all is fine so far.
They are definitely a known problem area on these grills. I love Weber grills (I have a NG Genesis at home too), but I am definitely disappointed in the regulator issues.