On the other hand, I've been using Fastmail for years, and on the whole it has been very reliable.
And, at least on my end, the outage appears to be over now. :-)
You might consider giving Fastmail some more time before ditching it, but perhaps your email reliability requirements are more intense than my own.
I think it's the fact that I was in the middle of some job-change-related communications that also gave me nerves. Generally my email reliability requirements are not very intense!
Overall I've been happy even with some of the things I've seen complaints about (Fastmail iOS app has been great for me despite mixed reviews). I'll give Fastmail more time before making a judgment.
(And indeed it looks like it's back online for me.)