I've got 4.4.4 on the N7 and 5.0 on the N5, so I can compare.

In general, 5 is better (faster, smoother, better-looking, easier, whatever) than 4 but there are a couple of regressions - the calendar in 5.0 is shit, and the auto brightness in 4 is better. I also don't like the new Chrome UI - I can see why they've done what they've done, but I don't like the way they've done it. Too much all-the-time functionality hidden away.