Imyrtseshem, I tried out the French track, to see what I thought of the artificial speech w/ something I perhaps could judge better than half-century-old Spanish. You have a point, for absolute beginners. It would be tough to try to acquire a first-rate accent from the TTS samples there. It would be FAR better than learning purely out of a book, however. When I finally get around to German, I know I'll be using LingQ sound files in order to introduce myself to the spoken German, and probably some old ba-be-bi-bo-bu sorts of recordings if I can find them. It would be nice if for the introductory stages duolingo provided recordings of native speakers for the initial stages, however, as you say.
But that's only for the very beginners. For me, who's heard both French and Spanish before, I found the sound files really helpful. They enabled me (or will enable me, I think) to work on some of the features of both languages that I have forgotten--written accents in Spanish, say, and all the silent letters in French, such as in verb endings or silent -e at the end of words. Spelling in general. Taking simple dictation. What a bonanza this looks to be. A limitless source of elementary drills.
And the translation "work" is also very good, if taken w/ a grain of salt. Some of their recommended translations (e.g.,79% of respondents . . . ) aren't quite right. Nevertheless, it looks to me like I could spend plenty of time w/ it. I did this morning, for several hours! If you give the translating a try in German, let me know what you think.