Hi.
I understand that the package can be helpful in some cases but its mandatory installment with npm has some bad consequences.
Please see npm/npm#20273
My environment:
OS: Windows
Node: 9.2.0
npm: 5.8.0

Briefly. When I run any npm command in a folder that folder by locked by additional node.exe processes started by update-notifier. That process hangs for a while and it's not clear what is it doing so long. So I have to kill it manually to be able to do anything with the folder. It's terrible experience.
Also it's hard to run npm programmatically. Executing child_process.exec with npm install for example hangs. I had to rewrite it onto the usage of spawn. But even with spawn we have to carefully use exit event instead of close as close will happen only after node processes spawned by update-notifier exit.

Also on Windows there're two packages:

• "C:\Users{User}\AppData\Roaming\npm\node_modules\npm\node_modules\update-notifier"
• "C:\Program Files\nodejs\node_modules\npm\node_modules\update-notifier"

It seems that when I run console under Admin account all both update-notifier's are running!