I switched from Gmail to Fastmail about a year ago after using exclusively Gmail for email since 2007. I've been very happy with Fastmail since then. Primarily I was bothered by getting the service for "free" from Google--it's not free for them to provide it (no such thing as a free lunch), which means they have to find ways to monetize my personal communications with others without me directly paying them. Obviously…
I disagree, I find it prettier than gmail.
Pretty much agree with everything else you said.
One con I'd like to add: GMail has send and archive and you can set it as default. I really miss that in fastmail.