Google translate has advantages and disadvantages. For a computer I think it does an alright job, especially for European languages, but it’s no substitute for a human and should be used in moderation.
A problem it does have is that when it doesn’t recognise a word, it won’t translate it. In fact, this can be a handy problem.
I often use google translate as a quick spell checker when I don’t have a spell check facility on hand. If I’ve written an email in Vietnamese for instance, I post my text in google translate.
I then quickly read through the English side and look for any words that haven’t translated. Most likely it’s because I’ve made a spelling mistake, so I can look at the word and see if it needs fixing.
This does seem to work better for European languages such as French or German, as a lot of the time google translate seems to skip over missing tones and translate it anyway. It can also be a bit hard to read through google’s English translation.
I’d still say you can catch some errors with your Vietnamese this way, though I do use it more for other languages.