I’ve been using them for a bit over a year now and don’t have any complaints so far. If you don’t care about the office suite, their email only package is €1.50/month for 5 users, which is hard to beat. You can use your own domain too. I like that their web/android clients have a proper conversation view that also shows your replies (like Gmail does). This has been missing from other providers I’ve tried (except Fastmail). Their android app is on F-Droid and open source which is nice. There were a few odd translations, like “Transfer” instead of “Forward”, but I think they’ve fixed those since. It’s not been long enough for me to comment on reliability or missing emails, but so far so good.