After having a full Tainted Satori run, I found out that Peerless Elixir ignores TSatori's speed cap, allowing her to reach very high speeds at 3 uses. The speed is so high that most bosses die in one hit from contact damage, the exceptions are higher health bosses and story bosses like Isaac or ???. Additionally, as long as you keep moving after hitting, you're most likely to regain invincibility back before losing eyeframes.

Not only the item basically allows you to win the run by itself, but also makes TSatori's birthright obsolete.

I think that Peerless Elixir should be adjusted on TSatori to either reduce speed given, or reduce how much it can raise speed over cap.