This is good for spelling and gender etc. but can be very frustrating when you make a couple little typos or minor mistakes and have to redo an entire level after making it almost to the end. It seems that mistakes near the end of a level have too much of a punitive function as opposed to rewarding good answers. Not sure if I will stick with this program because of this frustrating element.
After failing a couple practices and lessons today on the very last question, I do agree it can be annoying when you make such a subtle mistake and lose everything because of it, however I like how it forces me to make sure I am 100% correct, cause for me, personally, I don't want people to immediately recognize that I am not a native speaker of a particular language because I make small mistakes in every sentence. I just notice a lot of foreign people in my city think their English is top-notch, but I always hear small mistakes all the time, and a native speaker will hear your mistakes as well!
Don't despair though! This site has a really good community and my French has improved dramatically since I started. And in the site's defense, it's hard for the system to notice if it is a typo or if you just thought there was an extra "e" or something haha.