Whe you’re really happy with your FP, ther’s no reason to update.
Normally you don’t have to change a fine working system, only when some very bad security leaks have to be solved, a update is recommendet.
So enjoy your new Fairphone and have a lot of fun!
Honestly, you read some issue happening to a little % of the population, who may or may not be associated to this update, and if they are this is presumably because of the presence of other apps. What you didn’t read, and is equally important, is about the (vastly larger) rest of the population: because for them, the update just went fine. Me, for instance…
If you just start with you FP I’d advocate running all the currently available updates, because with no extra apps you are sure it’ll perfectly work.
I may understand someone with a relatively old phone and plenty of apps being reluctant. But with a new phone and no apps, go for the update. Plenty of us did it, it just works.
I’m in the same happy bunch of people as Herve5 - I haven’t had any trouble with my FP (1st batch) after upgrading (1.1, 1.3, 1,6 and the unified partition update). So the odds are good. But on the other hand, and generally, I do agree with Bobby: If it aint broke, don’t fix it! That’s a sound principle that has worked well for me during years of computing (Linux included). So I would say that you can safely put upgrading on the shelf and wait for the next one.