Resignation twist....
Doesn't look like anyone else here picked this up... when there was a close up of Frank signing his resignation letter the name printed under the signature space was "Catherine Durant, Secretary of State" (or whatever her position was). Frank is totally going to trot this out next season - surprise, surprise, his resignation wasn't valid, he's still the President. But, he can't do it until he's pardoned, which is why he is pressuring Claire to do it quickly. That's my theory, anyway.
I do agree with some posters here that this season was the least enjoyable. I was particularly upset by the treatment and death of Tom Yates. I think I had a bit of a "Tom crush" :(