I'm not going to lie, it looks impressive.
Personally, it was kind of a letdown for me on the PS3.
It's a good solid GTA game, don't get me wrong. But to me the thrill is pretty much gone at this point with just driving around a map shooting at people. Because that's what basically every GTA becomes after completing the main storyline. Hell, even during the main storyline.
Rockstar's open world are immersive in the sense that they do a great job of creating living cities. Well made, in depth characters, Pedestrians who interact with eachother, the games own spin on pop culture, in depth radio/TV stations with their own music and movies, talk shows, commercials, etc.
But they sure as hell aren't immersive in the sense of the player actually being able to interact with the environment.
The brunt of your interaction with the environment is sill going to be spent opening a car door.
One of my biggest complaints about GTA games has always been (other than San Andreas at the time) the lack of interiors. In what is supposed to be this incredibly detailed gaming metropolis, there are literally 8-10 buildings that are accessible in GTA V and that's including the same handful of clothes shops and the 3 main character safehouses.
You can't go inside of any of the diners or bars that you purchase as property later in the game, and you can't even go inside of the fast food places like Burger Shot or Cluckin' Bell anymore.
There's no more stuff like in San Andreas where you could break into houses and steal TV's and stuff for extra cash, territories to take over and build up your gang, etc
Maybe that will change with mods. I don't know.
Basically, both GTA IV and especially the new GTA V have definitely leaped foward in the technical aspect, but at the heart of the gameplay both of them still feel like a stripped down version of a game that came out for the PS2 hardware 10 years ago.