For a long time I have felt that using Google translate (or any other translation source) was cheating. Now, I have decided that it is ok to use it, and that I can take the original, the Google translation, and my own knowledge to come up with the best translation I can. I'm still learning when I do this. Please let me know, if you agree!
I think it is also a matter of the level you are at. If you are a complete beginner (less than 1 month for example) then something like Google Translate can help in getting the gist of an article so you know where to even start. But as you become more and more confident then it is far less necessary. In my experience Google Translate provides good idiomatic translation on only about 25% of the sentences on the Spanish texts, so it is far from a complete solution.
There are a lot of idiomatic phrases that appear in the passages to be translated that haven't been identified as such yet on this site, or often the exact meaning of a word isn't clear from the list of suggested meanings. In those cases, I'll try some translators to try to figure out the meaning of the passage. Sometimes there are terms that have no suggested translation (or ones I don't understand), and I'll do some research on wikipedia or something to better understand the topic and find the best English rendition (names, places, mythological beings, pop culture references). If you approach it from a learning standpoint, you can have a lot of fun discovering way more than just the language. And some side research (with translators or otherwise) can help a lot with the quality of the translations if you want to put that extra effort into it.
We're here to do two things; that's to learn and to contribute to translating the web. Google translator is useful for trying out constructing our own phrases to check if we're fully understanding things, and it usually has a long list of alternate translations for various words. Secondly, we want the web to be translated correctly, so using an external translator when we're not sure of a word or a phrase will be very beneficial in the long run. So I totally agree its not cheating as long as you're learning. (But if you're just copying and pasting paragraphs into google then thats totally missing the point)
Perfect example of this was a recipe I was translating. There was a term I didn't understand, Duo's suggestion didn't make sense - I think it was "chin straps" or something like that (I couldn't imagine cooking chin straps). So I checked it with Google, got "pork cheeks" - still wasn't sure, so googled (in English), "pork cheeks". Who knew? Turns out it's some kind of delicacy!
Google Translate is a last resort. It is very crude like all machine translation, so naturally you can't even achieve a good translation if you copy and paste its output. I often use Google image search to verify what on earth an unknown word or phrase is actually about. This helps in particular to translate idiomatic constructions (ie, most of real-life language use) or recent buzzwords in the target language.
I disagree with your comment on machine translation. I’ve been using Bing Translator to translate German letters that I receive, and it very quickly gives the gist of letter and helps me decide how much time and effort to devote to a letter. I find translation by hand is time consuming, particularly some of the wonderfully long bureaucratic words that are used, so a quick machine translation helps me decide on how much effort to expend on a letter. As for accuracy, so far I’ve found the translations make sense and are sufficiently accurate basis for action.
There is a way to cheat, But I never use it unless I want to know something really cool about the language i'm learning. You hover over the subject you want, and then put the subject name in the URL bar, while you're in another subject you already learned. It will look like this: http://www.duolingo.com/skill/fr/Family you are in family, and you want to go to adjectives 3.
you modify the URL so it looks like this:
And There you have the cheating system.
I find myself cheating when I get bored, if the lesson is making me learn vocabulary I'm not really interested in, or if I'm tired of getting repeats because of gender errors (I pay attention to gender most of the time but sometimes just don't care.) Usually I cheat by clicking on the prompt where Duolingo supplies the vocabulary word with its gender. I'll also use Google translate to get a quick gender, pronoun or conjugation.
One of my problems is that I love grammar and like to concentrate on verbs in language learning because you need lots of verbs to communicate and you need to be able to conjugate them. However, at my early level in Greek there's hardly any grammar and only a half-dozen verbs, so I'm trying to get through all the vocabulary which I know I won't use as fast as possible, in order to get on to the more interesting stuff.
I wonder what kind of data Duolingo picks up from users doing what I do?