I got the Blu-Ray edition for myself for Christmas, and I've watched the first two episodes. I'm really enjoying it. The black-and-white still photos from the 1930s come out wonderful on hi-definition TV.
The show is available for streaming, but it doesn't come out very well on my rural California Internet connection.

If you'd like to stream the show for free, you can start with Episode 1 here:

https://www.pbs.org/kenburns/country-music/episode-1-the-rub-beginnings-1933

For me, the Blu-Ray supplemental material was almost worth the price. There's a great interview of Rhiannon Giddens, for example.

-Joe-