I love Furious Focus, I take it as soon as possible. I love single attack character builds, I call it the "One Hit Wonder". It is my favorite character build but I am the only person in my group that even considers the build because I don't care about multiple attacks and everyone else in my group prefers to do as many attacks as possible. But to answer the question it is a must have for me but I do not see it as an overpowered feat, if it was everyone in my group would use it and I am the only one who ever uses power attack.
I can't tell you how much this post suits your avi choice - surely by design.
Furious focus is a well-balanced feat which I consider to be quite worth investing into - depending on what you want to do.
As others have stated, for non-full-BAB classes it's really good.
For full BAB it depends on what you want to do. Personally I always consider it for my characters:
- It's simpler calculation for the first hit
- It has made me hit things I might have missed otherwise. And really, you sometimes need to finish that opponent before he finishes your ally, and you need the damage from PA, and I *must* hit then.
- It's great when you have to move a lot.
- It's a prerequisite for dreadful carnage (great for action economy for intimidation builds).
Btw I think that comparing it to weapon focus is not adequate. WF binds you to a single type of weapon, FF can be used with almost all 1H/2H weapons. BIG difference :-)