TVG,
if you still keep an eye on this thread you may find that your m3u8 does not work any longer, I don't know why.
There is no need to complicate here, it works like this:
C:\>streamlink.exe
http://www.ustream.tv/nasahdtv 486p
[cli][info] Found matching plugin ustreamtv for URL
http://www.ustream.tv/nasahdtv
[cli][info] Available streams: 252p (worst), 360p, 486p, 720p (best)
[cli][info] Opening stream: 486p (hls)
[cli][info] Starting player: C:\P\VLC\vlc.exe --file-caching=5000