I had to look it up ... hadn't heard of it until now.
Is it worth watching?
Yes. The original movie is by far the best of the franchise--the heroine is a cyborg given to worrying about her own reality and quoting St. Paul. The sequel, ironically subtitled 'Innocence' is *very* dark, but not quite as good.
Of the TV series, I've only seen the first season. It was quite good, thought not up to the original movie--it does, though, give a reasonable conjecture of what a society in which the boundary between man and machine has been completely effaced might look like. Alas, one episode gives in to anti-Americanism with a truly loathsome American villain, and the introduction of a CIA agent as a representative of the American Empire. (Of course, that detail sort of charmed me, since post-9/11 I've decided I *am* an American imperialist.)
most definitely.
the movie made a bit of a hash of the plot of the original manga, but it was well worth watching.
the later series (stand alone complex 1 and 2, thus far) have, IMO, been more intelligent than the movie which spawned them.