I tried Duolingo a couple months ago (after the rework) for about a month and I can’t recommend it.
Some of it is purely subjective. I feel like their trial and error way of teaching can easily mislead you into understanding the grammar points incorrectly and you might often not realize what to pay attention to in a given sentence. The discussions under each sentence can help with that, and eventually I learned to just check those out often to make sure I didn’t learn something wrong, but with further and further lessons it got quite annoying how often people had to correct or clarify the sentences. However, your mileage can vary with this, everybody learns differently.
But my main problem with it, and the main reason why I eventually stopped using it, is their kanji pronunciation. Their text-to-speech system has a lot of trouble with kanji and the website doesn’t use any furigana. This means that at best, you might have trouble properly understanding how some words are supposed to be pronounced and you’ll have to go to the discussions to see the sentence in hiragana, and at worst you’ll learn the pronunciation downright wrong. Some words use a technically correct but should-not-be-learned-first pronunciations (like 明日, which it only reads as あす instead of あした), while others are read incorrectly in a given context (一人 was read as かずと instead of ひとり, which is apparently a name pronunciation, or 一日 is always pronounced as ついたち even when describing a time interval where it should be いちにち). And even when you’re matching pairs of kanji with their hiragana counterparts, the kanji is often read aloud differently than what you’re supposed to connect it with, even though this might very well be the first place you ever see that word in the course. So I just stopped before it taught me wrong things I hadn’t already learned before.
The one good thing about Duolingo was that one of the discussions about the kanji frustrations linked me here to Wanikani, so there’s that. 