I believe many people are not enraged for Unity trying to make money, but that they try to change their method to charge per install.
It currently to my understanding is this: if you are under 100k revenue in past 12 months, you can use Unity personal for free. If you are above, you have to use one of the subscriptions that start at roughly 2k a year. So very roughly, they are now charging like 2% ish of yearly revenue. Or less, if your game is popular.
As someone pointed out, if you have a low cost game, maybe free with ad revenue, you might clock in with millions of downloads. A hit like angry birds has 100 + million downloads. So even with the highest tier of only 1-2 cent per install we look at over a million $ in cost what previously was a couple thousand.
Oh, and from what I could dig up on their faq, the subscription fee for Unity pro + is still to be paid...
So, assuming a subscription of 10k a year and being "eglible" for that runtime fee. Having a tremendous amount of success and managing to have 1000000 downloads of your game is doubling your cost. It costs at least 1 cent, that is 10k. Oh, and if you manage to garner 2 million downloads, now your costs are not 10k for your subscription, but 10k subscription and 20k runtime fee. But 2 million are likely to get 10 million, making the yearly subscription only 10% of your costs, and having 90% of the cost being that runtime installation fee.
Small but successful devs might want to switch to an engine with more calulateable financial risks. As it is now, if you are not very careful, you might end up in a paradox situation, where success can spell out financial ruin for your gaming company.
There will be consequences. And there already are, judging from various news articles about this.