I gave it 7/10 straight after seeing it, but now I'd give it 8. I'd definitely watch it again.
I think it was more or less what I expected it to be so that was what was best about it.
I wasn't too happy with the choice of actor for young Kyle Reese though (Anton Yelchin - who incidentally was Chekov in new Star Trek). He seemed a bit too wet behind the ears - maybe that was purposeful (recap - Kyle Reese was originally played by James Cameron fave Michael Biehn). I guess by the time he comes back to protect Sarah Connor he's been hardened by warfare.
I thoroughly enjoyed the Marcus plot though. He starts on death row thinking, 'This is it'. I won't say any more. I'd go as far as saying that the actor who played the character (Sam Worthington - wonderful Aussie actor who's done his obligatory stint on an Oz cop show called Water Rats) outshone Christian Bale, who was playing typical over-serious, husky-voiced etc. He's a great character/method actor (check out The Machinist) and he fitted the bill of John Connor but his part just seemed secondary.
Bryce Dallas-Howard was ok. Not one of her best performances (who's she? Er, blind girl in The Village, Spidey's other love-interest in Spiderman 3 etc).
Moon Bloodgood was ok, reminding me of Tia Carerre (during her Relic Hunter days).
Overall it was gritty, it showed the devastation of post-apocalypse at the hand of SkyNet. But it didn't explain how, if the machines had crushed the humans and sent them scattering, the humans were still able to keep planes in the sky and a sub in the ocean (especially since there was no gas at the gas station).
I think there were too many sub-plots being used to make the story work.
Anyway, yes. Seen it, liked it, very enjoyable if you had seen the previous films (though I have never watched T3 out of protest lol).