There's no doubt GTA 5 is a beast and excels in nearly every way. But there are some issues along the way..
First off, the cops. This time around they mean business and even seeing one star can result in high speed chases and gun battles. In fact the cops are so efficient, it's almost pointless taking them on. Even at 2 stars, the police pose a serious threat and will ram/shoot you off the road if they get a chance.
That being said, escaping them is a lot easier also. Soon as the stars flash, which can happen if you speed off out of sight, you can then hide, even in a bush and the police won't find you.
But they still aren't the police I hoped for. They still sometimes manage to know exactly where you are, even underwater, when there isn't a cop in sight. They are still easy to aggravate too. You could walk down a road at 3am in the dark, not a soul around, and shoot your silenced weapon a few times in the air. You then hear screams from invisible people following by a one star rating. So much for stealth.
To echo the above, stealth isn't that, well, stealthy any more. As mentioned, silenced weapons seem to do nothing in the grand scheme and the police will be alerted if you have it suppressed or not. What a shame. It's also annoying, and I know it's an unfair gripe, but if you attack a cop. Instantly, before there is any radio backup, any witnesses, you get 2/3 stars. You should be able to kill stealthy, you can't. I had to steal a police truck, so I found one in a parking lot which was walled off. The only person inside was one guard with his back to me. I approached, knocked him out and instantly got 2 stars. How? It's moments like this which frustrate me and I know its not a fair complaint, but it does annoy me. The cops are really good shots also. Able to take you out as soon as you pop your head up. You can have full health and armour but one shot from a cop in the head, dead. For a game which doesn't focus too much on realism, this addition is puzzling. So many missions and shoot-outs failed because an enemy popped me in the head.
Auto aim can let you down too. Failing to lock onto an enemy. But most of my issues could, could, be fixed with a patch. But it's unlikely. If they were going to make the cops proper, they would have by now.
One positive little touch though is if you want to play the game properly and follow traffic signals etc, the car behind won't get impatient and ram you like in GTA 4. You can site at the lights and wait like everyone else. It's a small fix, but one I noticed right away, since it bugged me in the last game.
Overall the game is excellent, truly, but it doesn't deserve 10/10, 100%. Sorry, it just doesn't. But its a damn fine game, which I urge you all to play.