Also updated from 1.2.3 to 1.2.4 today, was smooth as usual. After upgrade ACP has some errors logged related to deferred. I deleted it instead of being smart and posting it here... but it was just during uploading files so I ignored it.
Upgrading xenForo is always simple and fun, never do you have the fear of anything going wrong.
I must admit I just did the same - system upgrade w/o a db backup... My host does automated backups ever 2 hours though so even if something didn't I would have been able to recover virtually everything anyway. Everything went smoothly regardless.