The game says I'm 45% complete. I own 7/11 cribs and lots of cars... I've messed around extensively with the customization of the character, the cars & cribs. Below is my current impression of the game.
* Customization of the characters, cars, your gang, and the cribs are awesome, even more extensive than SR1.
* Cruise control
* All sorts of real-time facial expressions.
* Peds aren't totally suicidal anymore (they don't readily jump into the street like SR1).
* Now there are motorcycles, helicopters & planes... and many more interesting vehicles. One I like is the "Bear" which you can steal from the police ~ it's an armored vehicle with a powerful machine gun on the top, and you can customize it =)
* Lots of fun things to do. Many of the old activities are still there, plus new ones.
* There are lots of interiors. The scope of the city, inside & out is impressive.
* Both a pro and a con ~ your character doesn't remove the body when killing someone and taking their car. Sometimes results in weird overlap... other times it just looks funny and realistic.
* Cars disappear and appear right next you... so if you spot a car that you want to steal, don't take the camera view off of it, even if it's right next to you. SR1 also had psycho car pop in/out... and I was REALLY hoping they would fix that for this game, they didn't.
* Customization is completely buggy, it often doesn't save or view properly. That goes for both the cars & the character (especially the character).
* Physics in SR2, or should I say "physics" is terrible. Everything about it is unrealistic. Generally this doesn't affect the fun-factor, but it would be nice to have some realism.
* Anybody can pull you out of your car, even if you're going 20mph and you're flooring it.
* Car handling is like SR1 ~ unrealistic. For those that complained about GTA4's realistic driving, you'll be pleased with SR2's arcade style handling.
* Car damage is as unrealistic as SR1.
* I don't remember exactly, but I'm pretty sure the police work exactly the same way - they know where you are no matter what, they can warp instantly, their cars are ridiculously fast, and the stars are removed by simply killing time (or going to Forgive & Forget).
* The game freezes (not often though). Save often.
... and a whole host of other bugs I won't bother mentioning. Some of them are huge, most small.
It's hard to compare this game to GTA4... I'd say it's more fun in the sense that there's more to do... but when it comes to technical issues this game is just sad. The thing that really bothers me is how cars disappear/appear so quickly and easily. That totally drives me nuts, especially when I spot a car that I want but I can't stop it immediately. Taking your eyes off of it means it's probably going to disappear.
I would recommend waiting till the price drops. This game is good (and better than SR1) but not $60 USD good.