Yeah, I just finished the season myself. It certainly wasn't as riveting or interesting as the previous two seasons. The show is still fantastic - it features some of the most incredible acting, cinematography and direction I've seen in a serialized program. Although something felt "off" - like J. Allen said, it lost some of that "zing".
I will say this, though: Without getting into spoilers, I really love what they did with Claire this season. I think it was during an early episode but they revealed something about Claire's intentions that we haven't really seen before. I thought it was brilliant. For the longest time, I had major concerns about the longevity of the show - although this season did little to quell them. However, with that said, Claire's character is quickly becoming my favorite of the show. It's almost as if the writers know this - heck, even some of the voters on the show were quickly favoring Claire over Frank. I feel like that might translate to the viewers of the show as well. At least, it did for me.
I'd have no problem if the show eventually shifted its focus to Claire, but given the ending of the season finale it'll be interesting to see where things go from here. I still think the show has about a season or two left before it might overstay its welcome. I just hope next season captures some of the show's intrigue and suspense more. Honestly, this season focused too much on the politics in my mind - in previous seasons there seemed to be a healthy balance between the differing perspectives, such as Zoe's perspective and then Frank's political perspective. Like others have said, Frank also lost a bit of his brilliant, ruthless touch this season - it's almost as if he was struggling to regain leverage and power throughout the entire season. I'm sure that was somewhat intentional, but it just made for a slightly different angle for Frank.
I hope next season changes or fixes that - let's see Frank trying to gain the upper hand again. Something tells me he's going to have a lot of cards stacked against him - pardon the pun - so hopefully next season (providing we're getting a fourth season - I assume we are) will bring back some of the show's signature zing.