To start off, saying that i am not in favour with the old icons, indeed i feel that they look dusted, don´t really reflect the vibrant UI look and feel of Yoxsemite color palette change.
That siad, i also wouldn´t go with the new ones:
As i see it, an icon should reflect what the app itself is able to help me with.
In best case it gives you a sense of the featureset without even knowing the name of the app.
I can´t really see how the new icons are doing that trick here. Usually simpler is better, but this looks more like an aged church glas window then anything of the topic here. I am not saying that they are not pleasing to the ey, they are, but they just don´t tell you the story.
An icon is much more than just branding.
And looking back to Adobe, i think those CC icons are just a plan b option: "as we can´t find a way of using iconography for doing the trick we´re now using abbreviations."
And as moentioned before, please don´t even consider to make an option for changing an icon via the preferences. Otherwise this would maybe even end up in a UI sandbox.
Sometimes in life of a UI/UX designer you just do those decision to focus on what you want to achive. In best case the 80/20 % rule takes account, meaning 80 % support what you do, 20% do not.
In my opinion Apple is a good example of doing icons which tell you the right story…
cheers Dietmar