I like Terminator Salvation because it looks and feels different from the previous films and although I was skeptical at the time, setting the whole movie in the future allows it to be its own thing. I think TS stands on its own but seeing the side of the Terminator universe we previously only got glimpses of is pretty neat.
Not saying it's perfect. The movie isn't exactly oozing with personality and the plot is too straightforward but it has more than enough set-piece moments and memorable visuals. Performances are good across the board if I remember correctly, even Sam Worthington who gets a lot of shit, was well cast.
I'm not sure how much the leak of Christian Bale's on-set outburst colored ppl's opinion of TS but after Terminator Genisys, I'm guessing TS' stock has only gone up.