If you have an "import from external system" ui/db rule and you try to pass a values like "[Code;OID]" it won't work. In that case you must set a custom text to [Code;OID] (this can be done with a ui/db rule) and pass this to the external system.
This change was introduced in SP21 and it is present on SP23. Other than that we have no troubles with SP23, though for reasons unrelated to it, in production we use still SP20.
But I've tested SP23 exhaustedly and found no problems whatsoever.