Well, after putting quite a bit of time into the game, let me say this first aside from a complete and total lack of variety (except for a first for the GTA series, clumsy stealth missions) the gameplay is fine. Nothing SPECIAL, but also nothing terrible. Some things like the way you can increase abilities is actually pretty cool, but it is all nothing you haven't seen before. Also the audio and voice acting is excellent.
Now here is my beef. Don't listen to any review that gives this game higher than an 8.5. The game has some major glitching problems that ruin the experience and should have heaviliy detracted from the review scores. To start with I am playing on the new mini-model PS2. The framerates are absolutely terrible. This isn't always a problem unless you are on a mission that A) requires you to move fast, or B) requires you to drive through a crowded area. At those points the gameplay slows to a crawl and you cannot even control you vehicle (that right there should bring the game down from it's near perfect review scores and put it in the 8+ category, if not lower) properly. This is a real pain on the motorcycle based missions such a Big Smoke's first mission where you have to drive a cycle through alleyways.
This brings up the next, and much worse problem, clipping. Take the above mentioned motorcycle mission for an example. Becuase of the framerate issues I have crashed the cycle quite a bit. On a few occassions, in order to avoid a total wipeout I tried to use the wal to slow myself, only to CLIP INTO THE WALL. When this happens you are then stuck in the wall and need to restart the game in order to get out of it. This doesn't just happen on this mission. I've clipped through many things while riding motorcycles around town. Also, while on a bicycle, I was hit by a car, and I actually clipped into the car and had to reset. It gets worse though. On 3 different occassions now I have actually clipped through the street while running. The street just suddenly disappeared and I fell through it and died. I also had this happen once when I was standing STILL, right outside of CJ's house. With these persistent problems in the game, they more or less ruin it if you run into them alot. Even if you only encounter them every once in a while, they detract from the game enough thatr it does not deserve the scores review sites are giving it. Consider this you best warning on the subject.