The chart has to be compatible with the unit, Garmin uses blue charts, standard uses cmap.
I use the bluecharts and love it. I've heard great things about the cmap as well.
If you buy the software it allows you to work with routes and review trips downloaded from the unit. I went with Garmin - the bluecharts for ~120 and a blank 32mb chip for ~100, ~40 for a chip read/write unit, works great and the usb give super fast transfers. You could also buy the chip pre-written, not sure the pricing.