I've been using a N10.1-14 for over a year and it's stuck on 4.4 permanently. I bought a Note 12 specifically because it's on lollipop. I always buy international (my Note 12 is from Singapore) versions of the Note so a lot of features don't apply to Wi-Fi versions or LTE versions neutered by the U.S. carriers. Here's why Lollipop was important to me:
1) I have a Note 5 and had a Note 4. Going back and forth between KitKat and Lollipop was driving me crazy.
2) Samsung's apps (EG: Mail, S Planner, S Note, Scrapbook, My Files, et.al) are over a year old on KitKat and I wanted the functionality and improved compatibility Lollipop versions brought.
3) Ease of use is improved. Samsung put TW and their own apps on a diet making them so much more consistent and faster at the same time.
4) Speed and fluidity is markedly improved across the board. Configured exactly the same way my Note 12 embarrasses my Note 10.1-14 even with pushing so many more pixels. Note that my N10.1-14 was Exynos and my Note 12 is S-800 which may have something to do with it.
5) Under the hood the Lollipop ROM gets a new kernel and all the systems re-engineering Samsung did for the Tab S. That's what's contributing to the performance increase and I'm getting fantastic battery life.
For folks that do the basics (e-mail, social, web, and entertainment) none of this probably matters. But I'm a big productivity user and compared to my Note 10.1-14 the Note 12 on Lollipop feels a full generation ahead.