I've just moved, and it's great. Import is fantastic (I migrated 14GB of email) and I've used Dmarcian to monitor and confirm everything is perfect on the SPF, DKIM front. Spam initially got through, but once trained it's been flawless I've personally abandoned labels for folders as I used barely 10 labels in Gmail and seldom added more than one, but they do support labels if you want that. It's great for wildcard email and aliases.
I've moved the calendar over too via Google takeout for the individual .ics files. On Android I use DAVx5 to keep using the Google calendar app (point it at your fastmail account and it will display in Google calendar).
For Drive I've moved to syncthing and am using a Synology NAS as my always online master copy, but each of my computers has a copy. I also installed libre office on my laptop.
And I'm keeping a Gmail account just for Android backup and app purchases, etc.