I have just completed the database conversion and faced some problems with the converter( IPS UTF8 Database Converter 1.1.19 ) that I want to report:
a) We had made in the past a backup copy of ibf_message_topics table to ibf_message_topics_old in our database. All our tables were already in utf8 so there was no need to convert their content, just the collation (e.g. from utf8_general_ci to utf8_unicode_ci). But, for some reason. the converter did not convert this table to utf8. When I renamed ibf_message_topics_old to ibf_old_message_topics, it worked!
b) we had a problem with a custom table which had a default value of "€" (Euro sign). This caused the script to exit with an error, since the "definition" column in table "convert_session_tables" that the converter creates was null! Tracing the code showed that the problem was due to the "json_encode" statement which returned an error "Malformed UTF-8 characters, possibly incorrectly encoded", when converting the field with default value the Euro sign. I checked the length of the field in my database and it is 3, so my content(and default value) is Euro in utf8. Since I couldn't find any other way to solve this problem, I had to temporarily change the default value (e.g. to NULL), do the conversion and then restore the default value back to the "Euro" sign.
Otherwise, the converter 1.19 works very well!