Actually Site5 is pretty good
Site5 would seem to very somewhere between "barely passable" and "what a deal" depending on your server.
From the support forum's outage announcements, It's obvious some servers are down much more often then others.
Rhodope for instance has seen service pretty much every week while (for instance) enki (or lithium) has seen an outage every few months while it rebooted.
What concerns me though, are the number of instances of "server came up read-only, we're fscking and hopefully everything will magically be better".