I've experienced some frame drop, specially in the big boring map stonehaven.

I'd say it probably dropped to 40 fps randomly. It also happened on other maps but less frequently. Have not played the SP, cant tell if any drop happen during campaing. One sure things is that the fps are mostly at 60 consistant and the few random frame drop, even though annoying, are not a deal breaker, I prefer the few random drop (that may be patch) then playing at 720p upscaled 1080

Digital foundry just put up a good analysis of why Ghost seems to has some issues on PS4.

"Taking the affected clips and running them through our performance analysis tools, we expected the results to show clear frame-rate drops and small bouts of tearing, but surprisingly this wasn't the case at all, with the results showing us a largely locked 60FPS bar one or two minor dips and a solitary torn frame. Furthermore, when seeking through the footage in performance-affected areas we were confronted with unique frames on a consistent basis, thus indicating a 60fps update that we just didn't feel when playing the game.

So just what is going on? Well, a close look at our captures reveals that Call of Duty: Ghosts actually runs at higher frame-rates than 60fps on a fairly frequent basis, despite the video output being limited to 60Hz. In scenes where we experienced judder and perceived frame-rate loss, what we are actually seeing is the appearance of skipped and incomplete frames - an effect that is arguably far more noticeable than a few prolonged drops down to 50fps or so seen the 360 version of the game."

http://www.eurogamer.net/articles/digitalfoundry-whats-fixed-and-whats-not-in-the-cod-ghosts-ps4-patch

It has been flawless and probably the smoothest game I have played on PS4 as of now. Of course 90fps will do that.