Road is in excellent condition in dry season
I just got to Humaita on BR-319 today. First 120-130 km are paved and last 50-60. There is a work going on on both ends, re-paving and new bridges being built. There is about 300 km of the desolate part. Most bridges were repaired and are in excellent condition now. There were only 3 so-so bridges, but they will probably be replaced soon too.
I spent two nights inside the Embratel tower fences (right by the fence). One night a truck came to check me out (I assume it was Embratel workers) and they didn't bother me, even though I clearly jumped over the fence.
There are 3 ferries over the rivers at the Manaus end of the road. They are rip-off, but it's not like you have any options.
There are traces of pavement even in the most desolate part. Apparently, the road was paved in its full length, once upon a time.
Not sure what it's like in rainy season, but in the condition I saw it, it's not a challenge at all.