I don't agree much with Gamespot's review: the game is not mediocre, it's not either a masterpiece, but it provides a challenging story mode, and fun side missions. But let's go in order.
Driv3r's story is mainly focused on the undercover cop Tanner, and while it's anything than spectacular, still manage to give interesting to the player. Tanner it's asked to join into a criminal ring that is specialized with car thief. You'll eventually be accepted by the group and start doing their jobs.
As undercover cop, your "friends" (the cops) doesn't really knows you while you'r doing the dirty job for the thief, so they'll chase you even if you are one of them.
The story progresses quite linear, once you completed one mission, you'll be thrown immediately to next one. There's little to explore while on missions, because most of them are time based or chases. The story take place on Miami, then moving on Nice and finally Istanbul.
Driv3r's new feature is not the ability to go on feet (that can be done on Driver 2), but to shoot. Sadly, this isn't Shoot3r, but Driv3r. The game fails to give a realistic feeling while shooting, you just make your way through enemies blasting them before they blast you. There are a nice array of weapons, but probably you'll stick with one and you won't be touching the others, FOREVER...
Speaking about missions, they give you variety: in one mission you have to chase an enemy, in the other one escape from the police, another asks you to keep a costant speed in order to survive, ect... Okay, now for the bad part: this game relies on your skills, if you aren't good at driving, you'll probably repeat a mission THOUSAND times.
The slippery car pyhsics doesn't help much on your efforts, so do the objects scattered on each road's side. What really matters is the nice car damage engine, unlike GTA games, the cars crumple up, and can lose wheels as well, making them impossible to drive.
The graphic in this game are a mixed bag, the cities are like their real counter-party, thanks to the immense job that Relfections put while making it, car models are nice too. The game features a weather/time system, this affects a little the car handling, but it changes the shadows and real time lighting! But that's about it. Graphically, Driv3r has tons of glitches, like bad clipping, cars that can get stuck on street lamps, clunky animations and framerate issues.
The audio part do its job very well. The music used during cutscenes are impressive, and so music changes according to the city, so just figure out how Istanbul is.
Voice acting it's also pretty good, though I'm italian so I cannot give you an exact feeling of the original actors.
Sound effects are normal, not too good neither too bad.
The worst part of Driv3r is the lasting appeal and bugs.
Driv3r can be completed even in 15 hours if you are good, more if you screw up (luckily there are some "checkpoints"). There's nothing to do after the story, you can always hunt down the 10 Timmy Vermicelli (pun to Tommy Vercetti, if you don't know who is he, kill yourself) and search the 3 cars in each city. But after that, you still get an empty game with some cool mini games, such as surviving, checkpoints, dribbling cones, ecc...
And now it's get worst, Driv3r is rushed, you can feel it, REALLY! There are tons of bugs: sometimes the AI goes random and totally ignore you, cops car get stuck on the same place, people/cars/objects... YOU... can glitch through the level and see the whole map. The best of them, is that there is an invisible hole near one of the airport ramps on Nice, if you fall through it with a van, and manage to land in the "green platform", you can drive till it ends and then you'll skyrocket and eventually land, and re-bouncing in air while spinning at crazy speeds.
So, after that, why I give 7.5 to Driv3r? Because the game is fun, if you get over the story, the rest is pure fun. Take a ride mode is your best friend in this game, and with cheats you can do lots of crazy stuff.
If you forgive all this bugs, you'll find Driv3r a funny experience, despite what people argue about that!