Holy thread necromancy. Guess I missed out in 2018 so I'll add my thoughts to this zombie of a thread.
I have read about increased back drag here and elsewhere, more than enough times to put me off on the kits. The price seems a bit steep too, but there are probably deals to be had if you're patient and look around. I'm not really that patient, and I also like to keep spare gut kits for my oft-used ratchets. Between those two things, it becomes too expensive for me to bother with it.
To each his own, but I have higher tooth count ratchets that fill the niche this retro-kit is targeted at, so for me it's sorta like a solution in search of a problem. I also dislike the selector design compared to the original. Call me crazy, but I also prefer the sound of the original mechanism to the buzzing of my other high tooth count ratchets. Last but not least, I'm not a fan of SK's quality control on their newer offerings. If their 90 tooth ratchets weren't such a **** show, maybe things would be different.
Again, just my $.02.