What areas have they improved in?

I was really disappointed by multiple Udacity courses; not saying they can't pull it off, but I've been burned enough by Udacity that I wouldn't consider paying for any courses from them at this point.

Yeah, I took most of the "AI for self driving cars" course taught by Sebastian Thrun himself, and was torn.

He's no doubt an extraordinarily competent researcher in his field, but he was clearly a beginner to Python (either that or he didn't care), and the Python code (while bringing the concepts across) was so poor as to be distracting.

I have watched a lot of Siraj's YouTube videos. He is a very entertaining speaker, but never felt like I actually learned a ton. Is the nanodegree on Udacity better?