Despite some technical flaws, Saints 2 has all the color, personality and fun of earlier GTA titles like Vice City.
The vehicle handling is miles more responsive and fun than its GTA counterpart, although almost every vehicle event that doesn't take place on land is just the opposite. Painful. The fighter jet especially is awful when compared to the fighter jet in San Andreas. One of the boat missions is close to impossible unless you get out of your boat and swim to a yacht for several minutes. That's not something that you're supposed to let stay in your game (instant death helicopter missiles).
There is also the issue of cars despawning if you turn around. Literally 10 feet from you, cars can just disappear if you face away from them for a split second. It's a pretty big technical flaw. Like I said though, the cars handle well and they are fun to drive, although there could stand to be more wacky trick ramps around the city.
Another issue is the falling mechanics, they border on awful and comical. Not only do they display the lower end of the rag-doll spectrum, they also can cost you your life from 10 feet off the ground. It doesn't help that your body just goes limp and rolls around sometimes, most notably during a final boss fight in which your character will (I'm not kidding) go limp and fall down every time the boss gets back up after you've knocked him down. He isn't hitting you at all, you're just going weak in the legs.
Despite the flaws though, it's well worth the $20 or so. Lots of excitement to be had, well crafted driving system, and an imperfect but entertaining combat system.