No hard data, sorry. I used it extensively until mid-2014 (I am now an expat) and rarely experienced any delays due to technical problems. "Rarely" means that

No hard data, sorry. I used it extensively until mid-2014 (I am now an expat) and rarely experienced any delays due to technical problems. "Rarely" means that I used it on average twice every day, including weekends, and I cannot remember more than 3-4 cases where we had delays (from 2007 to 2014)