ThisTV has had some cool movies, but almost every other subchannel has been worthless from my point of view. The MHz networks, including NHK, CCTV, RTV, AlJazeera have been an exception; though really I don't watch new shows, national or international.
There are a lot of different PBS channels here, but the main channels are what I'd watch and not the sub-channels.
One useful thing, for people with 20 year old TVs, is sub-channels with SDTV format so that things aren't down-converted. Again, doesn't help me