Only Simplified and not Traditional
I would love to use this product I really would but because I am not traveling to mainland china but to Taiwan where Traditional characters are the characters that are used this product becomes a completely useless study tool. Please make it so that you can choose which one you want to learn.
Please keep in mind that the Chinese course is in Beta, and courses in Beta can change. We don't know if Traditional characters are planned, but it's a possibility that is growing more and more likely due to the amount of people requesting Traditional chatacters.
Also, just because Duolingo teaches Simplified doesn't make it completely worthless to you. For one, several characters are the same across both writing systems. In addition, both sets of characters should be accepted within the Duolingo course as answers. (If not, report it.) If you want to learn Traditional characters, you can make note of the Pinyin and Simplified character and search for its Traditional counterpart online (assuming there is one) and memorize that instead.
The course isn't in Beta anymore but outside of Taiwan, simplified is widely used. I'd love to learn traditional as well but I don't think its worthless to use this if you don't know Chinese. Some words are the same in both traditional and simplified and others can be guessed. Furthermore the course teaches speaking so when in doubt one can ask, the Taiwanese are a friendly and courteous people. :)