I feel like I'm alone in being happy to switch to usernames. The 4-digit always seemed strange to me, and any time I'd ask someone for their name they'd always say "Oh, I'm name!", and then inevitably someone would followup with "What's your weird number thing?", and they'd say "Oh yeah, let me look it up".
Being able to use effectively the same username you use everywhere else is miles better IMO.
Maybe someone here can explain what was so appealing about the number system?