It’s done? It was still being built when I was there.

I haven’t ridden it yet but friends have.
Their pictures of the stations looks great, and they report good experiences.
Right now the new section is short, only three stations, and it is not being run as a new line, it’s an extension of the Q. When more stations are operational (next stop… Grand Central) it should get a lot more interesting. The whole line down to the Wall St area is expected to be completed in about ten more years.