My local Apple reseller has a much lower rate of foot traffic than even your smallest proper Apple Store, they have both the 1.83GHz and Black MacBooks on display.
Both are stock and both of them absolutely fly when dealing with the Finder, Apple applications and the few Universal apps. They bog right down when dealing with Rosetta as both only have 512MB RAM.
My Dad has a HP laptop, 1.8GHz Pentium M - it runs rings around my iBook and both MacBooks would not only run rings around my Dad's laptop when running Universal apps they would kick it and punch it until it gave up the ghost.
I suspect you may have been dealing with a machine that's had about a year's worth of use in a few months and hasn't had the luxury of a proper restart or even some basic maintenance. Those display models are put through absolute hell you must realise. The MacBooks I have seen are blazingly fast.