Buggy broken mess
I have been using WPML (Multilingual CMS package) for three years and it has never properly worked (even though they have a partnership with my theme of choice, which I've happily used for over 12 years).
The list of issues is long. It includes buggy UI, spontaneously disappearing translations, a lot of broken pages and terrible support. I feel like they intentionally make the support process so frustrating you'll give up.
Support is incredibly slow. They will also close support tickets without notifying you, so you'll then have to start the process of opening a ticket (which is also not easy, as I'll explain next) all over again. Most of the issues I raised were never resolved, so I stuck to my bandaids and work-arounds. I spent much more time on fixing translations and helping my confused translators than I should. My translators are perpetually confused by the buggy UI.
Since they've introduced AI to help manage support tickets, things are even worse. You'll spend (sometimes a lot of) time, detailing an issue, and in the next screen an AI bot will have rewritten your ticket, missing key details. Since your original ticket is not saved, all that work you've done is lost. So you then have to correct the bot and rewrite everything again. It's incredibly frustrating.
I'm currently looking for a way to get out, but our large website is pretty dependent on WPML. It'll be a big job to move to a new translation plugin, I but am looking forward to the day I'm free of WPML.
