Personally I went through the opposite process. I was a huge fan of Android up to and including KitKat, and I thought Holo was great. My enthusiasm for the entire platform disappeared as soon as Lollipop came out with the dreadful new Material UI. Even with themes I just hated using it on every level and eventually switched to an iPhone.
It was a lot of things around that release. The look, the feel of the "cards" everywhere, the deprecation of power-user features in the name of security (like full SD card read/write access for apps). Totally the right trade for a dumbed-down-but-safe mass-market OS, but that's not why I liked Android. When presented a wannabe iPhone I prefer the real thing :p
