During March, Komplex, a leading German hosting company site went through the month without any failed requests. Apart from Komplex, which runs Linux, the Top 10 places were almost evenly split between FreeBSD and Windows, with five of the top 10 hosting company sites running FreeBSD, and four on Windows.
Netcraft measure and makes available the response times of fifty leading hosting providers' sites. The performance measurements are made at fifteen minute intervals from four separate points around the internet, and averages are calculated over the immediately preceding 24 hour period.
Fuller information on the measurement process and current measurements are available.