I switched from Gmail to Fastmail back in 2013 [1] and haven't looked back. Fastmail has continued to make significant improvements, while keeping the interface lean and functional. It seems to me like $3/month is worth it for a service as critical as email. [1]: https://www.maxmasnick.com/2013/07/19/fastmail/ and discussion here: https://news.ycombinator.com/item?id=6069944
And they are making open standards (JMAP) and contributing to the Cyrus IMAP server.
Moreover, they will soon have labels :) (currently in beta).