They were poor and basic, but, after their initial teething issues, they worked. They only had a few issues with their rendering, but they were good enough for me. In fact I preferred them to the Google web apps.
Also, the article is completely wrong when it's saying "the app is in preview". No, it's not in preview, it has not been in preview for months. It forced you to switch from Mail and Calendar to it for a while, and you could only temporarily revert to Mail and Calendar, so you can't say it was still in preview, a preview would be opt-in and you could revert from it. That is until recently, now you can't revert even temporarily. It's New Outlook or nothing.
And, talking about not working, for the last week I couldn't mark emails as read with New Outlook in either of my 3 email accounts (2 google and one outlook account). I mean, I can mark them, but as soon as I do a sync they are marked as unread again. The latest update didn't fix that either.
Then there is sending email, where the email remains in the "sending" state for ages, when in fact it has already reached the destination. Then the duplicate drafts it creates for no reason, or the invisible drafts or emails that only show as a counter, but disappear when you click the folder. Then the UI suddenly displaying empty squares instead of icons. Then the crashes. Then the duplicate windows. Then not being able to click links in my calendar entries. Then sending empty squares instead of the pictures I inserted in the emails. It's a horror show.
Basically now I use the apps on my Android phone and tablet to read my email, since Windows is forcing us to use this abomination.