I'm a fan of the entire R&C franchise. I own all the games, and replay them regularly. Full Frontal Assault has been the most different thus far.
Gameplay mechanics are the same as the other games, so picking this up felt natural. Your weapons also still upgrade after repeated use.
The main difference in this game, is it's more of a strategy game than a platformer. The goal is to defend your home base against incoming baddies, while simultaneously venturing out to attack theirs. The bolts you collect go towards purchasing mines and turrets to help defend your base.
My complaint about this game was the length. There were only four planets, one of which you can beat in under 8 minutes. My wife (who is a complete novice to this and most video games) beat this game in about four hours. While there is mild replay value, having so few levels will get repetitive.
That being said, the game was a blast. I received this as a Christmas gift, so I didn't spend the money. But I wouldn't recommend buying it. However it is a solid renter.