Can someone who plays this confirm that
a) they haven't changed the cinematics
b) they haven't changed the music apart from re-recording it in higher quality.
Graphics wise this looks amazing, but for me sound, music and atmosphere mean much more.
It's ok. Music is the same, cutscenes are the original ones but in better quality (less pixilated). Mission briefings are the same except for the changed hero portraits obviously.
The parts where you had green text on black background explaining things are now accompliced by illustrations. No biggy, although I preferred it the old way. All in all it's very faithful except as I mentioned they could not resist to taint the menu artworks and some of the character portraits with their shitty SCII artstyle. Biggest offenders are the Protoss, who all got the "long snoot" make-over. Zerg and Terran have some portraits that are off too, it's especially jarring since other portraits are well done, perfect reproductions of the originals down to the last pixel.
All in all it's a good meal with a bit of shit on top.
Gameplay wise it seems faithful to a fault, you can't even use waypoints to auto-assign new workers to gather resources, just like in the original. That's how hardcore it is. I guess Blizzard knew the Koreans would rip them a new one if they tried any shit.
Ingame graphics are fine and completely faithful, although it takes a while to get used to the crispyness.
I'd say it's worth a buy if you can look over some of the fuckups in the art department. All in all it's probably the best remaster around and miles above shit like Age of Empires 2 HD.
Edit: You can switch between the original game and the remaster on the fly by toggling the HD Graphic option in the menu. So it's indeed just a reskin with the original game itself untouched, this is actually incline compared to all the remasters where they recreate the game in a new engine with all the bugs and fuck ups that inevitably result from that (Homeworld, Besmdogs IE remasters).