The only downside to that direct wired cable is the USB plug that goes into the Nuvi. They are notoriusly wimpy and if it fails you have to replace the whole cable with it's built in regulator.
Let me toot our horn here a bit - If you go with our TAPP Lite All-weather power port and GPS cable you get about the same set up but with a replaceable cable. And... you have a handy USB power port for charging your cell phone or other USB device.
The downside is that it's a bit more costly, but compared to most other motorcycle accessories, it's still mice-nuts and you have more functionalilty.
Both are available from GPS City.
12" & 18" cables are available as well.