We have the 540. We wore out our first model of the PC Miler - the buttons on it were inferior.
I have not used any othe brand of Truck GPS - this is is wonderful and suits us! It is easily customizable, you can plug in whatever you are lookig for (walmart, cabelas, etc) and it will search your vicinity and find all of them. It has several voices you can choose from but we have ours turned off (team). It also has customizable screen colors, displays, etc. It can tell you where the closest truck stop is - we use the CAT Scale choice as it eliminates the Mom and Pop fuel stops. Usually where there is a CAT scale there is a shower, LOL.
You can set it so that it always points North (handy), and adjust it to suit your rig - height, weight, type of tolls or not, hazmat, etc. We alternate between Destination view (so that you can see progress on a long run) and 3D next turn.
It spins around if you decide to ignore it and make a turn anyway and will guide you the new way you have chosen back to the best way (detours, In and Out stops, etc.)
If it gets emotionally challenged by asking it too may questions at once there is a handy reset button on the back.
Well worth the money. Saves arguments. Prevents accidents opening up that senior citizen large print laminated atlas we all have to have over 50.
Hope this helps.
Kat