I imported from 1password. I found the following problems.
- Some items did not import correctly at all because the 1password export format did not quote values (CSV). This means that if I have a password with a comma in it, I get two broken entries. This is more of a 1password issue though.
- 2FA tokens did not import and would have to be manually reset. I guess this is to be expected though.
- Some fields had different names than bitwarden was expecting, so values were imported into the wrong destination and had to be manually corrected.
This was a while back so I'm not sure if anything has been improved.