My 50 cents here... First of all: this will never be 100% safe. Mistakes happen to you users and to us developers as well, nobody is perfect. Add to this that this is built upon bugs and holes in Nintendo's own FW and that there can always be strange hardware quirks. Take, f.e.
this guy, and note (if you're too lazy to read the whole post) that this is a hardware problem, not one of Decrypt9.
That being said, if you followed Plailects guide in the past by the word, and used OTPHelper, even one of the problematic releases (v0.6 ... v0.63), you did not encounter a bricking bug from our side. If it failed, it failed because either (a) my safety checks correctly detected something was wrong and made it stop or (b) my safety checks wrongly detected something was wrong and made it stop. In both cases, before any damage was done. In fact, we do have a pretty high success rate (keep in mind, users are more likely to report in if they have a brick).
Now, to do it, or not do it? Ask yourself, how bad would a bricked console be for you? If it would be your absolute nightmare and/or you have no possibility of getting a hardmod in case of things going awry, let it be, or at least wait for a bit (this might get safer in the future - no guarantees, though). MenuHax already provides a good enough solution for most users, and waiting an additional 20 seconds upon boot should not be of too much trouble to most users.