As others already said, Nokia account has the single biggest benefit of syncing your favorites(between different Nokia devices) and also navigation routes between web based nokia maps and your nokia device. (Ex: You found navigation directions on Nokia's "Here" maps site and I think from there you can save that route to your account, which will then show up on your phone.
Other advantages are: Nokai beta labs, nokia music(which actually doesn't require any account for basic streaming), nokia transport, etc.
It wouldn't hurt to have Nokia account. I am still using my Nokia account from symbian days.