I've been using Gare du Nord for onward/return travel off and on for almost
30 years and I cannot recollect ever feeling totally at ease while
crossing Paris - be it by RER or the normal metro service.
Just buying a ticket can be a headache in itself, with few machines
operational and the ticket office usually manned by just one person,
despite major queues forming.
Thankfully, the automatic service is showing signs of improvement,
with easy to follow instructions in languages various now installed
close to the ticket office.
But one massive gripe I have is the lack of staff at the automatic barriers,
with nobody on hand ever to help those with luggage and children as far
as I can recollect.