I know that even amongst the rocky track record of the Terminator_franchise, _Terminator Salvation is not especially well-liked. I've always been a little bit of an outlier when it came to this series though; like everyone else, I know the first two are the only great ones, but to me, it's actually not T2 that stands at the top of the pile, but The Terminator, the first film. And since that first film, we've copped 5 new runs at a Terminator movie. Out of all 5 of them, Salvation is the only one that tried something different from the first one. Even the lofty success of T2 was garnered using the same core concept as the original movie. Salvation hits something new, and while that obviously doesn't work for a lot of its audience, for me, it's the best movie outside of the first two that the franchise has made to date.
Final rating:★★★ - I liked it. Would personally recommend you give it a go.