Skins are divisive subject. Do they really matter? Are they literally evil incarnate? Is TouchWiz actually that bad? Well, now we're going to vote on it: will your next phone rock the stock, or will it be SenseWizwhateverLG'sthingis-ified?
For the purpose of our poll, "major" UI layer modifications will include a pretty broad range. Anything made by Samsung, LG, Sony (yes, sorry, that is a "major" skin), HTC, Huawei, ZTE, and a number of other OEMs that is not a Nexus or GPE device is considered "skinned" for the purposes of this poll. Motorola devices, Nexus devices, GPE devices, OnePlus devices (CM adds many functions, but aesthetically is / can be made very stock-ish), or any other phone that runs a version of Android with extremely minimal (or straight-up Google-approved) modifications will not be considered "skinned" for the purposes of this poll.
As for you ROMers out there, there is a poll option for your situation, don't worry.