my c340 unit be the first and only gp device I have ever use . I do quite a bit of research , read review and advertisement , ask other rv ` ers etc. . I purchase it primarily for use in my rv , just complete a 4500 mile trip through the US Midwest and Manitoba and Ontario . it be great , fall off the windshield once but I think that be my fault . after make sure that the suction cup and windshield be clean , that never happen again . I download the instruction manual prior to purchase , but the unit be so easy to use that the manual be not necessary . it could be improve in locate highway rest area and rv park . some be some program . we cross area where gasoline station be as scarce as hen 's tooth and the c340 be great in locate and guide we to gas station , a couple be off the highway and could not have be find with out the c340 . some of the feature I like most be a -rrb- if you misunderstand or miss what the voice prompt say , it will repeat : b -rrb- it can be use as a compass and speedometer . it will tell you you exact speed and direction : c -rrb- ease of use . on the negative side , once in a while , a turn instruction be too late but after I learn to pay a little more attention to the screen information , I find that I have plenty of time to be ready before the voice prompt . most of the time there be adequate notice . when a turn be miss , it immediately tell you how to correct the course . thing that would make it even better would be : entire route planning and display include estimate drive time and distance . for example , if I be plan a trip from Pittsburgh to Dallas , I would like to see the entire route and estimate drive time . of course that information be readably available other place . and Garmin do advise the user to use the c340 as a guide , not the sole input . for the price , it can not be beat !