Make no mistake, they killed the lore.
I see a lot of complaints about protoss in this thread, and I'm not sure I get it. Are they really that different from sc1?
Well. The Tal'darim weren't too bad, in the context of the xel'naga plotline. Then again, that plotline was lame and gay. I was so stoked after that SC1 mission with Duran and the hybrids - they could have spun that in a number of different directions. And this was what they chose.
Some of the changes are a direct result of this. The interesting thing about the Protoss has always been their culture, this fanatic mystic warrior cult theocracy, kind of like a mix of Knights Hospitaller and Shaolin monks. Very collectivistic. In LotV, they all leave the Khala and end the caste system. You could say that individualism runs like a red thread through all the SC2 campaigns. It's almost like some kind of evangelism. I'll just say this: If you enjoy that sort of shallow sermonising, let me point you to some books by Terry Goodkind.
Not many significant changes lorewise apart from that. That doesn't matter though, because presentation is one half of story. And boy, is it bad. The dialogue is like something lifted from a bad fanfic. They dropped the ball on the casting of voice actors, too. Pretty funny when you come under attack, and those slow, measured voices unhurriedly notifying you of this urgent situation - "Esteemed Commander. The enemy has initiated hostilities at the perimeter of your base of operations. It is strongly advised that you react to this situation with hostilities of your own, honourable leader. After all, is it not true that brave warriors of noble lineage are dying as we speak?" Unengaged and unengaging. Just like the rest of the campaign.
Some other minor nitpicks: I'm not 100% sure, but if memory serves protoss are supposed to have two opposable thumbs. Most of the people in your war council have pauldrons on their pauldrons. Artanis even has an extra set of pauldrons hovering above that. Protoss engineer guy has a beard, wtf. Their animations are pretty funny too - everyone's constantly swaying back and forth and shrugging their shoulders and pumping their fists. Fenix in particular looks like he's having an epileptic fit in slow motion. Why are some warp blades green? A warp blade is a warp blade. For that matter, why do Amon's forces have a Sith reskin? Is it his evil that makes things change colour?
And Zeratul used to be cool.
A few other things worth mentioning. Why do the characters in SC2 campaigns get so emotional over dead marines. They're basically violent criminals serving out their sentence as an long succession of suicide missions, all the while pumped full of various drugs that make them go insane over time. A marine that survives long enough will probably be reduced to a drooling wreck. Pump and dump is the idiom, I believe.
Was also pretty funny towards the end, when the xel'naga tells Kerrigan she needs to merge her essence with him, and winks his four left eyes slowly at her. It's just a part of the animation cycle, but I found the timing very amusing.
But hey! They brought the reavers back. Silver lining to every cloud.
In conclusion: