This worked for maybe 20 minutes, but after that, any time I so much as plugged this unit into the car's outlet, the car's fuse would immediately blow (even with nothing plugged into the inverter).
The concept is great, having a place to put the inverter that is convenient and doesn't dangle or shift around, yet also isn't a big device that has to plug right into the accessory outlet (which isn't always placed to facilitate a device like this, and also precludes being able to simultaneously use the outlet to power anything else.) And enough people have left good reviews that I assume they're not all so prone to quick failure. Nevertheless, I will not buy another PowerLine. I previously had the PowerLine 0900-36A which also failed (though I did get more than 20 minutes out of it). So I just don't consider them reliable, and I don't know how long other reviewers have had their units.
Luckily, there are numerous other cup-holder-sized inverters to choose from, just do an amazon search for "inverter cup"
UPDATE: I purchased the Black & Decker PI100CB. It only has one outlet instead of two, but at least so far, it's working perfectly. It is possible that the Powerline failed quickly because of a design flaw other reviewers have noticed... the Powerline needs air around the fan toward the bottom of the unit and that air flow will generally get blocked once the device is actually placed in a cup holder, possibly leading to overheating and failure. The Black and Decker has a clever design which solves this problem. It comes with a rubber insert that goes in your cup holder, and the device in turn goes into the rubber insert. The smart thing is that the rubber insert itself is designed to make sure air flow to the device's fan is not blocked.