I don't do well without audio
I started the Irish course and liked the first part of it, and then I started getting sentences without audio and new words without audio. I guess I am a very auditory learner because I can't get vocabulary to stick without hearing it. I understand they are using a new system and they don't have recordings for all the sentences yet, but if they have recordings for each individual word and you could hear them on mouseover that would be great. I may put off Irish for a while longer until it goes out of Beta or maybe I'll just learn how to pronounce irish words and say them outloud all the time like I do with other languages.
Check out forvo.com or focloir.ie for pronunciation. I personally recommend the latter for Irish, since it has pronunciations for each of the dialects, but forvo has all sorts of languages. You can also expose yourself to the sound other places. I've been listening to music on songsinirish.com and it has the lyrics, so you can see what's going on with pronunciation there. There's a fair mix of music ranging from traditional sean nós to modern pop. There are various other Irish language listening resources out there, too, although I haven't dug deeper than music quite yet.
"Buntus Cainte" is cheap and available on Amazon. It is a beginning Irish course that is almost all audio. It is a good complement to the Duo course.
Mango for Languages has every phrase recorded and you can mouse over single words in phrases to hear them, record your voice and compare it to the recorded voice both aurally and visually. It's a subscription service, but in my town our library subscribes to it which gives any card holder free access to it. It was the system that got me over the Irish spelling/pronunciation hump and I've never turned back.