It’s hard to give statistics which make sense, with multiple locations, and dozen and dozen of VPS on multiple servers, but this is roughly what we get.
Basically we took the downtime for each VPS in minutes, divided by the amount of minutes X VPS quantity X 365 days.
The majority of our VPS have 100% uptime, and some of them had few minutes because of a network problem or an hardware issue.
It will be a challenge to do better in 2013, but who knows :).