As embarrassing as it is to admit, I primarily use Duolingo in bed with a wireless mouse and keyboard. The mouse slides around a lot with the sloped surfaces, if on a flat plane and doesn't work so good right on the bed, so it's kind of a pain to use. Which is why I would love for the lessons to be completely keyboard centric.
Right know is really good. But unfortunately I'm not far along enough were I only use the regular voice recording (which have a shortcut to replay Ctrl+Space Bar). I actually have to hear the slow version quite a bit, which requires mouse use. So it'd be great if everything was done on the keyboard. The multiple choice can be answered with 1, 2, and 3, which is great, but the picture answers aren't (hopefully I'm past those).
I don't expect hovering over words to know their translations and stuff like that to change, just enough to "take the test"
Not a big deal, I know I'm in the minority on this, few surf the web in bed. So not expecting too much, but if it can be done pretty easily that'd be great.
In order to replay the audio slower, use CTRL+SHIFT+SPACE.
In order to fill out the correct word for a set of pictures, just type the article and it will automatically populate the dropdown. Granted, this may make it slightly more difficult than simply picking a correct choice, but it is definitely doable.
Replay audio slower is ctrl+shift+space (see http://www.duolingo.com/#/help), but you can only navigate dropdown menus with arrows if they are the only question. If you need to fill out article with a dropdown menu + type the word, then there seems to be no way to navigate the dropdown with the arrows.
I think Duolingo does a great job on the keyboard support, and certainly a better one than others. My only suggestion on this would be to be able to do EVERY step via keyboard.
For example: When I finish a lesson, I can press enter, space, the numbers, so anything I used during the lesson, but it still won't bring me to the next lesson. Just a small thing, but it would make it much more intuitive for keyboard-lovers like me (yes, I am an Emacs-user and Starcraft player :D )