Then Ultron becomes a comic book bad guy and breaks all the rules the movie just showed us. And it showed us these rules a minute before, dammit.
I went on a bit about Transcendence, but I did it for a reason: there was some good stuff in there. Fun concepts and interesting questions, all torn apart by trying to make us side with terrorists against a really stupid genius.
That first scene of Ultron coming to life is beautiful and the mind boggles at what such a creature would be able to do.
Spoilers (assuming you haven't watched the trailers): he creates pointless cannon fodder robots and throws them at the heroes, who he knows will have no trouble getting rid of them.
I really liked this movie, and I get why it had to be the way it was. A proper AI which followed the rules of that first scene would destroy the Avengers with ease, and that wouldn't be a very fun movie. It would be able to use whatever technology it could get its hands on, which includes anything Thor (who told us his magic hammer and Norse afterlife is all just advanced science), Iron Man (because duh), or anything in the Shield arsenal.
More though, it would create things that are even better and then everyone would just have to shut up and do what it says.
It was programmed to bring about world peace and it would do so in a few hours (a day, tops). Or, more likely, it would reprogram itself to get rid of stupid directives like that and go to space to hang out with Rocket Racoon and Groot. Because those guys are awesome.
So instead he behaved like any other bad guy in a comic book movie. Oh well.
The movie played out like a short story, though padded out a bit with robot porn (which still played to the plot, to be fair). The ending was obvious a mile off, but only because it had been handling the AI well the whole time. You can extrapolate what's going to happen because you can trust in the rules the narrative set up right from the beginning.
The movie is great too. It's a character movie with three people in one house, and I'm a sucker for stuff like that (see When The Gods Wish To Punish), and this is handled well. The tension rises as the film goes on and the payoff was perfect (even if you see it coming).
It's a cool film and you should go watch it. There aren't as many explosions or Iron Mans (the plural of Iron Man wouldn't be men), but it's a fun little ride.
Read a book (he says, knowing he just went on about movies for ages. Again)