As simple as the device is to use, it has a few problems that I didn't particularly like. The first is one that just goes with all adaptors in general; in some cases, it's not the most travel-friendly thing to use. It's good if you have somewhere to plug it in, but what do you do if none is available? While it's good for use in the car or at home, it's a little too limited to make into a primary power source.
Also, the cable is way to short. It's just long enough to be of use if you're in the front seat of the car (preferably not the driver's seat), but it doesn't reach to the backseat.
The battery cover is also a pain to insert as well. Pulling it off is as easy as pressing the release button, but it's a battle to put it on, and sometimes when you think you've gotten it on, one corner isn't in place, causing you to start all over again. The same goes for pulling the AC plugs out of the adapter - it's not as much of a struggle as the battery cover is, but there is some resistance and things aren't as painless as they could be.