My macbook downloaded the Mojave update and presented the question:

to update or not to update?

TLDR: no issues on my MacBook Pro (Retina, 15-inch, Mid 2015) except for Little Snitch 3 which is incompatible and I had to upgrade to version 4 for €25

Hardware

MacBook Pro (Retina, 15-inch, Mid 2015)
Processor 2,2 GHz Intel Core i7
Memory 16 GB 1600 MHz DDR3
SSD 256 Gb
Graphics Intel Iris Pro 1536 MB

Installation

The update took about 30 minutes and that’s all I have to say about that.

Apps

After the update Mojave I first updated the Logitech control center since it was the only app reported to be incompatible.

Then I looked at Little Snitch, because of the error message “Not supported OS X version”. The download button took me to the version 4 update which is compatible with Mojave. The upgrade license was €25.

All other apps just worked or had an update pending. I was most happy about Camtasia 2, Parallels Desktop 11 and Alfred 2 still working since those apps would make the update to Mojave to expensive in licenses. I would have restored my Time Machine backup. Check https://roaringapps.com for compatibility of your favourite apps.

Hick-up

During boot I notice a hick-up. After the progress bar under the apple logo gets to about 75% the screen flashes. A lot of people have noticed it.
One time when I booted in clamshell-modus with an external monitor on mini display port, the progress bar took about 2 minutes to completion. But I never noticed it again after that one time.
Normal boot time is 30 seconds.

Why upgrade?

1. I want to have my macbook running the latest and greatest macOS.
2. New features like continuity camera and quick look edit can be handy (Whats-new)

Update

Little snitch rolled out an update in december 2018 that fixes the hick-up