The game can look great when it wants.
But then it can also look like crap. Given this is an AAA game, sometimes (too often) texture's quality is abysmal. There are also times when you can notice low-polygon objects here and there; e.g. I saw octagonal barrels in one of the Easter Europe chapters (due to lighting and shadows you could clearly see sharp edges).
I've already saw some nice moments when the game utilized it's new lighting engine (the scene in Leon 1, just before the third train in the sewers, where you see zombies' shadows on the wall) and levels are much larger than they were in RE5 but man, you can clearly tell that overall graphic quality took a nosedive when compared to the previous game. Even explosions don't look as great as they used to.
Finish the prelude. Completely. It shouldn't take very long, and you'll know when you're done with it when you then get the option of selecting the 4 campaigns.
The whole thing with prelude was very weird. I was confused when the game required me to setup my graphic settings and then suddenly started Leon's scenario - without giving me an option to select a chapter, select a character, change keyboard settings or do anything at all. I suppose it must have looked even weirder on consoles, where all you can do before starting the prologue is change the brightness.
I'll echo Riposte's tip: Try sliding past the enemy and pulling back on the analog stick mid-slide to instanteously turn around so you can blast them in the back. For even more fun, try doing it when they're crowded around a barrel.
And for EVEN MORE fun, drop some remote mines on the ground at their feet as you sliiiiiiiiide past them.
KA-BOOM!
And don't forget sliding into the cover.
The cover system in this game is really clunky: go near the wall, press aim and then press action button to take cover (too many times I managed to forget about the "press aim button" and simply jumped over the cover). But sliding into the cover really helps.