My Alfine 8 has given me no issues and the changing of gears when stopped is nice when one forgets or has to come to an emergency stop.
One can't compare the Shimano vs Kindernay or Rolhof as the latter pair are in a different league in quality and pricing. One can buy 4 or 5 Alfines for the price of one of the others.
Nexus 7 on our Motus behaves very well. As Nealh says, change of gear when stopped is a big benefit. (In fact, we chose the hub version after my wife got caught during a test ride on a derailleur in high gear after a pause at the bottom of a hill; restarting was very awkward.)
It does need a complete stop of pedalling for 1/4 second or so to change gear, just backing off pedal pressure doesn't seem to be enough. Easy and not enough to lose momentum on a hill, but something extra to have to think about.
Gear range is much less than a typical derailleur system. Plenty on a crank drive with adequate motor. I wouldn't want the Nexus 7 on our tandem with (underpowered for a tandem) XF07; we often need a much lower gear then the Nexus would give with any reasonable chainring.
The Enlivio hub is also interesting, wide continuous range. I've never ridden one, and it too is much more than the Shimanos, though not nearly as much as a Rolhoff.
Used derailleur systems since 1960.
However first time I tried the Volt Infinity when I bought it five years ago I found the Alfine rear hub system a revelation.
As stated a second of pedal pressure easing during changes is beneficial. The ability to manually change at a standstill is excellent although mine does this change into second gear when stopped automatically.
I will change the bike eventually and I have a beady eye on the Gazelle C380 with the aforementioned Enlivio hub and belt drive which looks the business.