The Mark of Mafia series is defined by the fact that the interface is a little clunky, but much more involved. The design actually has gameplay that is a little more focused and complicated and separates itself slightly from the pattern set up by previous incarnations like iMafia. Gunshock Racing really works to break through this model by adding quite a bit flare in the form of pictures and new names, but still falls into the trappings of the Mark of Mafia franchise.
There is nothing overtly wrong with this game, and in reality it has a lot to offer in terms of depth in gameplay. You will find that it actually has a more difficult learning curve than games like Race or Die and that there is a little more going on than in most. Does this make it successful? In a moderate way, yes. The problems that were inherent in Mark of Mafia are still here, yet there were serious attempts to clean them up.
There is still a large bit of lag in the system and commands take a while to come together. This makes the idea of quickly checking in with the game a little difficult. At the same time the interface is still a little dull and there is confusion all around. The differences between this and similar titles are all around, including the requirement to level up to get into all aspects of gameplay.