I think the key question is what happens after the first year? How much does it cost after year 1? If you don't pay will it brick your PC or just stop providing updates?
I didn't hear anything about a subscription on the stream, but the stream is buggy, so maybe I just missed it.
But what I understand is that upgrade will be free if done in the first year, like the 30€ upgrade to Windows 8 in the first few months. If you don't upgrade within the first year, you'll have to buy the new Windows.