FWIW, my experience mirrors Lake's.
Our first trip was October 2011 and we felt like masters of the FP system. Loved it! But that's when they still allowed people to come back after the FP window had closed. That system, with those rules, was awesome.
Our second trip was October 2012. Still with legacy FP, but they were now enforcing the windows. Honestly, that wasn't a big change for us, because we really did stick with the windows for the most part even when we didn't have to.
Third trip...short SWW trip with legacy FP, first weekend of June 2013. I can go back and find my post, but by using the FP system at an optimal level, I know we did something like 15 attractions in the morning alone at the MK one day.
Fourth trip...October 2013. FP+ was in the early stages of testing and the paper system was still available. We used much, much more paper than the FP+s because the FP+ system was so crappy. The
MDE app kept crashing (I remember uninstalling and reinstalling it every day). While I don't feel like MK touring was affected that much, I did feel like we accomplished less in the other parks, particularly Epcot. In 2011, we had 4 rides on Soarin'. In 2012, that came down to 3. But in 2013, we got ONE, and that was with our FP+. There was a big glitch in the paper FP system (some might remember this) and it caused all the paper FP+s to be distributed within an hour of park opening. On past trips, paper FPs were available well into the afternoon hours. The same thing was happening with TSM, but we were to the park early on our DHS day, so I was able to pull paper to supplement our FP+, so we still got three rides on TSM.
Next trip was a 3 day trip in August 2014...this was our first full FP+ trip. I felt like I spent far, far more time planning ahead of time, learning about the new system, figuring out how to optimize it, etc. Again, I can go back and look at my schedules and compare them to the past, but I am certain that on our MK day (comparing apples to apples here) we accomplished far, far less than we did in June 2013 because we were using SB more and only used our 3 prebooked FP+s, plus two more (I believe...I'd have to check). In August, I was relatively satisfied with the system, but the parks were also dead, especially the MK.
Our last trip was in December 2014, the week before Christmas (13-20th). FP+ seemed like it took even more pre-planning than in August. In August, at least I didn't have any problems securing the FP+s for the times I wanted, but it was a different story for December. And then I felt like I had to keep an eye on the boards because Disney started dumping more FP+s into the system. In the end, after hours of changing things around, I was happy with our pre-booked FP+ selections, but it was frustrating to get to Disney and have no opportunity to change anything, and only have total crap selections for the 4th FP+. We accomplished far, far less in December than on any prior trip, especially via FP (in other words, our FP+ was far lower than our FP usage was in "the old days.). Epcot--we used our three FP+s and that was it. One ride on Soarin', no rides on Test Track. DHS--again, three FP+s and nothing else. We still got 3 rides on TSM one day, but we did SB for two of those rides. MK...once the park got crowded after 10:30 or so, we accomplished very few rides. The first 2 1/2 hours (park opened at 8:00 a.m.) were golden for SB. We'd do SB for the first couple of hours, then switch over to FP+, and then...just hang out (thank goodness for SOMK). The SB lines were too long and there were no FP+s available. On December 14th I was able to finagle a FP+ for POTC as our 4th selection, but that was back at the resort after playing around with MDE and finally getting overlapping spots for the 4 of us. One other day that week I was able to finagle a Mickey FP+ as our 4th (again, with overlapping times) and we waited 25 minutes to meet him, which was aggravating (posted SB wait was 35 minutes). Other than that, it was SB because there were no FP+s available for later in the day.
So we've definitely experienced a significant decrease in the number of attractions we do because of the FP+ limitations.