What a beautiful language is Hindi!
I can't say what the reason is, but I find Hindi is a very beautiful language. Also it is rather easy. In case you try it you'll overcome soon the initial difficulty with the syllabary. I am at about 70 percent of the course and it is a nice excursion. It is somewhat exotic for Europeans, yes it is. It opens a gateway to a very important part of the world though.
I also like Hindi. I waited for the course since I joined Duolingo (3 years ago) and I was happy when it was released. Yes, it is quite exotic even thought it is an Indo-European language. I think that the Devanagari script is beautiful and there are a lot of sounds that do not exist in many other languages (like aspirated and unaspirated versions of some consonants, nasal vowels). The grammar is also interesting.
I knew very little Hindi when I started the course but I know some Persian and it was nice to see that Hindi has a lot of common words with Persian (some are actually of Arabic origin but not all of them). I am also at about 70 percent of the course so I will probably finish it soon and I hope there will be an extended tree one day. But I think that the quality of the course is very good, which is more important than its length.
Really beautiful and quite easy ! I completed the tree, but I had a lot of previous knowledge. Now I'm watching a tv series in Hindi and I learn something in every episode and I feel like it's much easier to recognize the new words in Hindi than for example in Chinese or Russian. In Chinese and Russian I feel that despite being on lower intermediate level that it's extremely hard to distinguish some words that I haven't heard before.