I really enjoyed the game, but I thought there were plusses and minuses in every category (no spoilers).
Gameplay - I loved the traversal and that's a lot of what made the game fun. Running in the game is actually painfully slow, which I assume they did on purpose. String together long runs with grinding, bouncing, wall running and air dashing is very satisfying and they littered the world with so many things to use that is was very easy to keep moving and get across the world quickly. On the other hand, the places that traversal was used effectively in missions were few and far between. Many missions were "kill everything" missions, and while you need to use traversal effectively to keep your style level up (and survive), what I really wanted were chances to prove mastery of the traversal system with platforming challenges. The timed traversal challenges were a welcome addition, but I would prefer non-timed platforming requiring you to use all the skills to make it to a hard to reach area. Insomniac has done this so well in their platformers, I was hoping there would be more of it here.
Collectibles - an extension of gameplay, really. I think they could have done a lot better here. Insomniac platformers in the past offered a lot more challenge and a lot more reward for collectibles. Also, while you could get hints to help you with finding they collectibles, they never just flat out gave you a map. Way too many collectibles with very little reward. and that includes the reward of just being challenged in collecting them. This is especially for the non-currency collectibles.
Story and dialogue - the story was sufficient for the setting and feel, but really nothing special. I actually enjoyed a lot of the dialogue. There were a lot of pop-culture references and fourth-wall breaking that made me laugh. They may not hold up in the future, but they work now. As I mentioned before, I also really liked the female voice - she had great delivery, was very likable, and fit the character well. A lot of the other characters had their moments too. Where I thought they dropped the ball was on the over-reliance on "haha they're nerds" jokes and the incredible amount of swearing. Yes, it's an M rated game, but sometimes less in more.
Weapons - the weapons were a lot of fun, especially in combination with amps and overdrives. and there are a ton of them. I only maxed 5 weapons during the game, and that was with consciously switching off. After finishing I swapped out pretty much my entire inventory to work on other weapons (I focused on single shot weapons during my play through and switched to automatics) and I still haven't purchased all the weapons yet. On the negative side, they didn't really differentiate between each weapon as well as they could. Something notable about the Ratchet and Clank series and the first Resistance is that each weapon has a purpose. You'll have a long distance weapon, a weapon that's good at killing multiple enemies, but only up close, a high powered weapon with limited ammo, etc. In this game there seemed to be a lot of the same weapon type with slightly different effects. For example, the fireworks gun, the teddybear gun, and the hairspray bomb all do kind of the same thing with some minor differences. Same for the taunt bot and turret copter. It was nice having all the guns, but it was rare that I felt I needed to use one specific gun in a certain situation. Overall though, the weapons are great and this is more of a comparison to thing Insomniac has done a little better in the past.
The MP is fun as well and is worth a try. It gives nice rewards for a well co-ordinated group (although that can be a challenge with randoms).
Overall I really enjoyed the game. I don't know if it will be my GOTY, but I have no problem recommending it, especially if you like chaotic shooters, games that don't take themselves seriously and 3D platforming.