We/Our customers also use informix. We also use postgres a little bit too. The company was a startup about 15 years ago. Actually, looking at your past comments, looks like we may work at the same company.
ditto ...
Nice to see there are still some Informix users alive! :) We are dying breed for sure, don't see any new solutions being developed lately. Too bad. Anyhoo, we also use Oracle, MS SQL and MySQL.