How I love posts from users who claim they're IT professionals and who keep returning their 4200 units because for them the speed increase is important and link trustworthy sources claiming double-digit performance increase... it's just a pile of BS, you know
I think it's a "mine is bigger than yours" thing. If a 4500 equipped model would suddenly appear, i bet they would moan at the nearest BB and request yet another replacement, poor souls
For newcomers - no matter what cpu have you received - as long as your unit (the Surface!) is okay (no excessive bleeding, no faulty components), be happy with it and don't read threads like this one.