To put it simply, Buy this game: ADDICTING GAMEPLAY & LEVEL-UPS, IT'S FUN, PLUS PROMISE OF DLC. Forget the haters.
As you already know, there are five skills: Agility, Strength, Firearms, Driving, and Explosives. All of these are fun to level up and takes time. The bosses are easy to hard based on which gang you face and what level you're at when you face them. For instance, if you face Shai-gen, a gang that is brutal, not so friendly, while adding killer skills in explosives, and your at one star with explosives, 2 stars with strength, 4 with driving, 2 in firearms, and 3 in agility,. then your chances of beating them will not be sogreat. The people who zipp who these bosses more than likely have their agent leveled up to it's peak with the most powerful weapons (auto-locked rocket launcher), then yeah, they'll be a breeze. See it's all a matter of how you play it.
Plus there are a ton of agility and hidden orbs lying around in obscure places and on rooftops. It's a blast jumping from building to building like Morpheus in The Matrix when he was teaching Neo how to leap. In addition, your able to increase your skills in strength. This allows you to hit objects and people harder as well as throwing them a great distance. The more you level up each skill the greater the agent is. Trust me, you'll feel absolutely invincible once you leveled everything to the max. You can't but to feel like a superhero after you gained the ability to jump very high and land cracking the ground underneath your feet. When you land from a jump and crack the floor after escaping from dozens of enemies, you'll understand exactly what I mean. Also you could cause random fun damage with your friends (in Co-op) by piling up cars and exploding them, or by doing foot races to see which agent is the most athletic. There are endless possibilities you can do if you just think. A lot of people don't want to think and that is why there so depended on a mission structure to guide them. The dossier popping up when you're close to boss, dropping you the info, is fine and the Narrator who talks (a lot) while you play is such an interesting dynamic. It makes you feel like an agent. And if you don't want to hear him you're able to turn his voice off in the options. Check it... this is game is basically about you being a genetically powerful agent who is created to be superior than the ordinary cop to take out gang members littered all throughout the city. You're not a gang member, and this is not a story. If you buy this game looking for that then no doubt will you be disappointed. Thinking like this is like going to looking for a girl to marry. If you go to a club then expect to leave with someone who loves going to clubs. Don't expect a wife. So trust me and buy this game if you're open to it.
Oh and by the way... I give the sound a 9 because there are so many sound effects they put in the game that it's crazy. Try throwing an explosive canister around and hear the sound. Or try throwing a car around and notice how impressive the sound of its physics sounds as close as the real thing.