I bought a Garmin 1490T for a New Year gift to myself; reviews for that revealed that there was no mains charger included in the package, so I ordered this as well.
It turns out that the 1490T comes with charging cables for use in the car, and a combined data/charger USB cable, so I can easily charge up my 1490T both indoors, and in the car. Hence I've never even tested this charger.
May be a great device for you, but do consider whether you really need it -- I certainly don't.