I did mine this weekend as well. I figured this thread was a sign that I needed to just do away with the excuses and do them. Took me about 16 hours, spread out over 3 days.
I think they came out really well, especially considering I never did box braids at all. Actually, I think it is a good idea to start with yarn. You learn the technique,with only three strands of "hair" and then you can graduate to real hair.
All in all, I'm pretty satisfied with how my hair turned out. Here are a couple pics. (OMG, it took forever to figure out how to resize them