I am a 3.5 player and can feel a difference. The extra reach on serves and groundstrokes are unmatched, but my net game suffered badly. Once you get use to the extra swing weight that comes with the extra length, it probably won't make that big of a difference. I think my problem was mainly psychosomatic. If you continuously switch back and forth for an extended period of time, it will only amplify the differences. This, of course, is only my humble opinion. Try it and let us know your thoughts. It would make for an interesting thread.
How's my night owl friend doing these days? For me, I could never get use to extended length racquets even though I have given them a shot a few times now. I ended up losing a significant amount of swing speed on groundstrokes but I do agree with your assessment they do give you a nice pop when serving.