Not to be rude, but "doing fine but they weren't able to grow" sounds like PR bizspeak for "unable to sustain themselves". It isn't like Opera is a company that can really grow Fastmail when they haven't even done that with their browser. I don't see how you could particularly trust Fastmail to be around for an extended period when they were recently sold to company few would consider stable and healthy.

Then again, I don't really see the point of not using Fastmail as long as you can export your stuff.

They explain the rationale for selling in a couple blog posts. They were a really small company, only 3 or 4 guys. They didn't have any "PR bizspeak" people. They were profitable for 10 years but didn't have the resources to expand into business accounts. It sounded like the meeting with Opera people was kind of a fluke.

It's the same reason I don't switch apartments even though one might be better for the money: it's a hassle.