On a side note, all facilities (and not just Linode's) will experience issues from time to time. You want to evaluate the manner in which it was resolved and the frequency. Don't move because of one outage in the last several years and degrade the experience for your customers. If an outage is going to damage your business then you should investigate high availability and/or quick deployment strategies.
All of that being said, if your users are mostly US based you probably won't notice the latency between any of the US based locations.
London is the best in my opinion because I get the best latency to it (not surprising - I live < 50 miles) and its had 0 outages since I've been in it.
They're all equally reliable in my opinion, Fremont just got unlucky. Every DC is going likely to experience some form of major outage throughout its lifetime. If you're running anything serious you should have redundancy in another DC so it doesn't matter if your primary fails anyhow (your primary will fail - don't ever assume it won't just because you picked a "good" DC).
I chose Fremont in the past because it's the lowest latency to me.
Now, however, I have a website that I want to place in a separate data center from Fremont. All the other data centers in North America are about the same latency to me. So latency doesn't really enter into the equation _for_my_this_particular_case_. I figured I'd just choose a data center based on perceived reliability, and perhaps proximity to the 'center of gravity' of the Internet (whereever that is).
But ...
I wanted to make the poll general so it's more useful for future readers. Hence the resultant wording.
The only thing that matters is location — both for latency to you and your users and, perhaps, if you dislike US or GB laws.
The only other difference is that the Atlanta data center used to block numerous ports (most notably 6667), but that doesn’t seem to be the case anymore.