it means users don't have to have to have multiple logins and stuff
Agree.
Login issues with SF makes me crazy.
Also about that 99.9% people have no troubles - I assume this is a people that have SF account - they are lucky. But you just cannot get opinion from those who has no SF account (e.g. me:). I'm sorry but SF authentification system is BS. It's very buggy and slow. I used SF earlier through Google but recent time I lost my account because of changing authentification policy.
Unlike SF GitHub has good cross-site authentication system and I don't care about it.
-- Best regards, Pavel Roschin aka RPG