If I saw a plumber driving around Atlanta with www.AtlantaPlumber.com on his truck, #1 - it'd be easy for me to remember, and #2 it'd be a more positive than negative perception of that business.
I used to own a print business with a .net domain name. We'd often tell a new customer our e-mail address at the end of our first phone call. But too many times customers would just type .com in the e-mail address and then assume that our business has lousy service.
After a few months I paid a cyber-squatter (if that is still the appropriate term) $1600 for the .com version of our name and I never regretted that decision.
yes.. this..
side story, a friend of mine owns a city dotCOM name that also has a university with the corresponding .edu..
He receives email regularly from students pleading (to teachers) for an extra day for thesis completion or a gpa bump : )
One thing I would mention is that many people know that names like "BikeTours.com" were the first to be registered in the early Internet days, and these days do carry a degree of trust through age.