Adding conversations to the skilltree
I'd love to see a focus on more conversational sentences. Maybe add casual everyday conversations to the skill tree. For me that's a lot more useful than learning hundreds of new words.
There are a lot of courses with a main focus on everyday conversation. One of the reasons that I like this course is the fact that it teaches you so many words that you can have a real conversation. There are some good conversation starters that you learn in this course.
"Hola, come estas?" "Cuantos anos tienes?"
Some people might even ask how many children or pets you have so those phrases may come in useful, too.
If you are realy focused on coversational phrases you might try http://www.123teachme.com/learn_spanish/conversational_spanish
And use it as a supplement to Duolingo. I always recommend using multiple language courses to study. You can't become fluent from one language course. Maybe some day in the future. But right now, that's pretty much impossible.