There’s a strong warning associated with the “One Mind” upgrade that says that “it’s all downhill from here”. As I’m still interested in playing, should I take this upgrade or wait?
Will appreciate spoiler-free answers if it’s at all possible.
Having played quite far and having read the source code, I can tell you that yes, you should purchase “One Mind”. The “downhill” is part of the fun and the narrative of sorts and the negative effects aren’t that bad given the many benefits.
All of the upgrades to the grandmothers beyond that point are very effective at raising your CPS/grandma by sizable amounts. This purchase adds the risk of Golden Cookies (the randomly appearing cookies) sometimes having negative effects like losing cookies or temporarily lowering CPS. It also adds a new positive effect that the golden cookies can give as well. The game also adds “wrinklers” which are randomly appearing creatures that will lower your CPS, but once destroyed will yield 1.1 times the amount they consumed so that actually makes them a good thing.
With the exception of some very rare events that are handled separately, all golden cookie events are equally likely so even with all the elder upgrades purchased, you’ll still get positive effects about half the time or more. It starts out with negative effects happening about 1/6 of the time after the purchase of One Mind and gets worse later.
Once you purchase all of these elder upgrades, a new, repeatable upgrade can be purchased to stop the negative effects from happening for a time. Once this repeatable upgrade has been purchased enough times, a toggle upgrade to revoke the negative effects indefinitely can be purchased at the cost of some cookie multiplier. If you ever want to get back that multiplier along with the negative golden cookie effects and wrinklers, another upgrade can be purchased to toggle back.
Given that many of the later upgrades and buildings begin costing in the trillions (100 trillion for several of the upgrades), you’re going to want to go for as much CPS as you can (balancing cost/CPS as you go) so that you can let it run in the background, collecting for you. Checking in every now and again and clicking a golden cookie (or several in the case of a chain) is worth it too because it can save you hours in the long run.