To be short, for me it was a very logically-lame movie. CG and visual effects were great, but the plot, and 'inner logic' were terrible.
Giant robots who fight monsters with their _fists_? Minimal pilot safety, ridiculous mech designs, _heads_ on those mechs, no AT rockets, no flamers, almost no cold weapons. They could electrify mech's outer plating, could give them long spears with AT-charges attached to their tips, could do hundreds of things to improve mech's combat effectiveness and survivability. But no. Instead of a high-tech weapons, mechs in 'Pacific Rim' are walking chunks of metal, so fragile that a single blow can tear off their hands.
About Chinese Mech and its pilots. No evil Chinese communists who want to conquer the world this time? What happened to you, Hollywood? You took Koreans for #1 villains instead? So, Chinese folks looked decent enough. Too bad that their badass mech had so little screen time. It was awesome. But I think that it would be more logical *Spock's face* to attach an auto-cannon to every hand instead of those chainsaws with little to no damage against those monsters. And their fighting tactics... I know that kung-fu looks cool, but a kung-fu robot battle with saltos and stuff? It looked quite strange. I mean, why bother? It'd be much easier just to take a giant stainless steel club and beat that monster to death. And I don't believe that all those geniuses failed to invent a badass machine gun with armour-piercing rounds for those mechs. Still, Chinese guys were awesome.
Few words about so-called 'Russian' mech. Depiction of Russians and their technology in that movie was at the 'bullsh*t' level. Those 'Russians' in the movie looked more like those comical 'evil Russians' from 'Red Alert', with beards, fur hats and trained battle bears. Hello, US film/game makers, socialism is no more. Cold War is gone too. So stop f*cking around and start depicting Russians properly. Really, I feel sorry for that nation. So many years have passed, yet US government still pours sh*t on their heads 'just in case'. So, 'Russian' mech. Are you kidding me? That slow steampunk-ish piece of crap is all that Russia could provide? Really? Even nowadays Russia is one of the leading countries in weapons development business. (Ehh, Germany, stand up and keep up) I doubt that that situation would change in the near future.
Australians were kinda cool too. Especially the dad. He was a badass.
No German pilots. Why? I don't demand a special mech for them (oh well, actually I do). I just wonder why do we have Australians, Chinese, Russians, but have no Germans in that movie? It's twice as strange because, as was said in the movie, Germans helped to create that 'Jäger' (Hunter) project. Hell, they even had a Japanese girl as a pilot. I demand Aryan presence to be included in the sequel. )
Back to the logic failures. Again, inefficient close combat weapons, almost complete (only ONE Jaeger had 'em) absence of rockets, no mine fields, no aviation, no cruisers/air carriers, no gun placements on that stupid wall they built, no tactical nuclear weapons, no powered blades, no decent pilot cabin armouring, no breathing masks for _all_ pilots, no ejecting safe pods for _all_ pilots, ignoring of drag when Jaegers fight in the water, no backlash pain inhibitors in pilot suits, no decent radar/sensor systems on Jaegers, ridiculous armour plating with many weak spots and unprotected areas, people still live near the water, no tanks, no artillery, no tank-mounted plasma cannons, no chemical warfare, no high-ex bombs, no remote-controlled Jaegers, no mass riots against useless governments, and many other 'no's.
This movie contains great visual effects, but aside from that, it's quite mediocre, and sometimes just stupid. (It's my opinion, and it may be different from yours)