I don't know how significant they are, but I can tell you that I have been prescribed prednisone twice during marathon cycles, and whether it was the effect of the drug reducing all inflammation and eliminating all aches and pains or just the placebo effect, I absolutely destroyed my workouts during the prednisone cycles.
I did the same workout two marathon cycles in a row 4 xx 1 mile with 1:00 rest, 5:00 rest, then 3 x 1 mile with 1:00 rest. The first time I did it, my splits were: 5:12, 5:20, 5:16, 5:21, 5:13, 5:17, 5:24. The second time, during a prednisone cycle, my splits were: 5:15, 5:08, 5:13, 5:12, 5:14, 5:14, 5:14. The second effort also had a lower perceived effort even with a 5 second per mile faster average pace. Maybe some of that was familiarity with the workout or improved fitness, but some of it was also just feeling really good from the prednisone (again, perhaps as a result of the placebo effect).
Whether the OP feels guilty or not is up to the OP, I simply said that I wouldn't feel good about a PR set while using prednisone based on my firsthand experience with it.