I never have lettered my trucks, mainly to avoid tons of worthless estimates from people out of my normal area. Here were I live and work, I could find enough clients within a 5 mile radius of my house to keep 10 crews busy... I don't need someone from the other side of town driving by and seeing my number, to call me and bother me with requests for stuff too far away for me to go do.
Who knows, maybe it wouldn't hurt to have signage, but I have done just fine without it.
2008 Toyota Tundra
2009 Wright Stander RH 52"
2008Scag Tiger cub 61"
2006 Husquvarna ZTR 42"
Stihl BR600 blowers
Kawasaki/ echo handhelds
37, Married, 7 year and 1 year old sons , Solo operator, Average 60-70 accounts, mostly residental, Been in business since 1994
When not working I am either flying, boating, jet skiing, or riding my motorcycles
Here is some videos of how I enjoy my time off http://vimeo.com/user2428477/videos