"Thanks and good night!"
अनुवाद:धन्यवाद और शुभ रात्रि!
I have only heard शुभ रात्रि as well. It might be more due to convention as शुभ रात्रि is a phrase from sanskrit. रात is the अपभ्रंश of the sanskrit word रात्रि and is used in general conversation. I think that it should be translated as a phrase and not word by word. We have a similar situation with शुभ प्रभात , it is a phrase that should not be translated as शुभ सुबह or शुभ सवेरा। . This might be more due to the phrase sounding right and less with any grammar rules.
Well, I too have heard शुभ रात्रि. But frankly, I've only heard it on TV or on very rare occasions. In my daily life, I've never used it at all, because I use Hindi only in informal situations and everybody just prefers to use 'good night' or other English greetings itself, instead of शुभ रात्रि or other Hindi greetings.
You are right about that, people just say "Good night". our team gave considerable thought to such usage and we didn't see much value in teaching the learners mere transliterations. The course is about Hindi. Also bulk of this content will be useful on the reverse course too. Our philosophy has been about teaching Hindi and not transliterated versions. With the reverse course, there's not much point in teaching an English speaker on that course to say good night as "गुड नाइट".
There are exceptions, such as bread, which means रोटी, but also means a slice/loaf of bread - ब्रेड. it is also accepted as डबलरोटी.
Please be patient. The Hindi team are working so hard volunteering their free time to create the English for Hindi course, which now has over 100,000 learners. Once this course is out of the beta stage it is probable that a Hindi for English speakers course will be added into the incubator which then may take several months to create. So perhaps a realistic aim is that by the end of 2014 there will be a Hindi for English speakers course, but again please be patient it may take longer than that. There are many other excellent resources online to learn Hindi.
Also you can turn off the listening skills by going into your settings and changing the Speaker option to off. Or in Hindi मापदंड > स्पीकर > ऑफ > परिवर्तित रूप सहेजें.