Never had problem with the London datacenter. I was on Newark before hand and I don't remember having many problems (maybe 1 or 2 times in a couple of years).

Avoid Fremont at all costs (unless you really need a server in that location), its been like this for years.

Dallas is much better than Fremont. I moved all servers after their first outage months ago.

Word on the street. We are migrating to Dallas after this is resolved.