I have been silent for a while and I am not going to jump in the more dramatic pieces of this thread (or those on other sites) - just don't have the mental time or energy for it (heck, the Warriors are going to a Game 7 and that is taking all my mental energy right now ;)
Since it has been asked, I am the member where 7D sent me an L01 with specs I was somewhat shocked by. To their (and Chris's) credit, they always offer to remake for free within that early time period. Since I hit the shaft and learned more about what I wanted (and not wanted), I made another L01 that is more 60SX and is working spectacular (I mean, really really well).
I have not thought hard on how the 55SR came about and not going to (these things happen, maybe it was a design mistake, maybe when I said I want a baby draw, they used the flex and weight to do that in the design phase, etc). This is hard over a questionnaire and email, but no different than blindly buying any other shaft instead of going and getting fit in front of trackman (but 7D, at least with their design process, is probably better than blindly buying).
I have owned a Standard, Distance, Control, re-made a Standard, 3W, re-made a 3W, hybrid, L01, L01 that I didn't like and a putter 7D shafts. They are firmly in my driver, woods, hybrid (and putter) now. With 7D, yes, maybe they will mess up here or there, or maybe the design won't be what works, but they have fixed that multiple times for me.
My advice, pay attention during the design phase. Stay true to the questionnaire (i.e. do you really carry it 260 or is it 240 + roll), do you really have a baby fade or is it more of a 15-yard fade ;), etc. Pay attention to the design that comes back, look at the stiffness, weight, profile, ask questions, etc.
Now onto the second-hand 7Ds. needmoregolf hits my Control shaft longer than I ever did and longer than what I currently game. Maybe its the shaft, maybe the swing, maybe the *improved* swing, or all the above (I say all the above - he killed me last time we went out ;) If you know your specs, you somewhat know the bend profile that works for you (and that head) and how that connects to the flight you see and want, I don't think getting a 7D second-hand at all is that bad, but like everything, its hit or miss. I know my other Standard which I sold has been passed around a bunch, so maybe that hasn't connected to someone yet, but to each their own. That exploration, tinkering is what makes all this fun!