I picked up Sleeping Dogs with some expectations to it. I heard it was a good game and it plays a bit like GTA. Ironically I found it to be more fun to play than GTA (probably because the gameplay was a bit more to the point and was not ridiculously difficult at certain points). Take that with a grain of salt however since I am not the biggest GTA fan out there.
Other than that, the game has much to offer in terms of modifying your character, buying vehicles, and a ton of extra content that will keep you busy if you don't feel like burning through the story. There are race missions, martial arts fights, favors and a ton of random things to do in the city.
That being said, the only gripe I have about the game is that it is pretty easy. As you progress thru the game, I found myself asking why the developers bothered with certain aspects of the game such as the food stands and favor-missions. I guess just to add flavor to Sleeping Dogs.
All in all, I DEF recommend you give the game a shot.