Wikipedia reports that the great Downgrade controversy began with Charles Spurgeon's first "Down-grade" article, published in The Sword & the Trowel in 1887. Spurgeon maintained that his brethren within the Baptist Union had effectively "down-graded" the Word of God as such heresies as the Graf-Wellhausen hypothesis, Charles Darwin's theory of evolution,
and others crept in to their thinking, thus weakening their position on sola Scriptura.
The great Downgrade Controversy of Logos began in 2012, when poor marketing choices went into effect to "down-grade" the upgrades of L4 users to the new L5 package names.
I absolutely love the new features of Logos 5! Especially the Bible Senses Lexicon, and the Timeline (something I have wanted to see since Logos 3 came out). I absolutely despise that my upgrade from L4 Portfolio to L5 Silver, sounds like a down-grade in name. I wish Logos would do something about that--so that my About Logos Bible Software window, under the help tab, would reflect "Former Portfolio (L4) Owner, Now Overlaid in Silver (L5)." [That would help me deal with my pride issues.]
But make no mistake about it, I have lost no resources, no functionality, and zero dollars of any previous investments in my study library have been lost. The new features are amazing. And I expect Logos will continue to develop the product into even greater things in the future. (I do hope they do a better job of marketing, however--paying close attention to the old adage: "An informed people is a happy people.")
While I never enjoy paying for an upgrade, Logos 5 (IMHO) is worth every dollar I have spent on it.