I use mine every day since December, '09 with a wall charger and have had no problems. I have also used it with the Nokia car charger that I got either with the N800 or with the N800 Wayfinder mobile kit. I can't remember which right now.But again, no problems.

What I can't do is use a USB car charger to a Nokia USB to small pin adapter (CA-100), and then the CA-146C. Even a desktop USB connection doesn't always light up the N900...

With all that said, to answer the question about whether it is just a decorative item, no. It is useful in my "real word.

However, I have seen pictures of ones that have melted so I suspect there is a bad batch.

If you are having problems with it charging when using either a standard Nokia car or wall charger or you fell that is heating up excessively (warm is ok), My advice is to stop using it immediately.

Motorola and RocketFish make car chargers that fit the N900 and that I used, both work well, and both are about 2/3 the cost of a Nokia one and may be easier to find depending on your location.

The Motorola unit I use even has a push button LED flashlight on the USB end. The RocketFish is smaller and has a shorter, lighter cord that may put less strain on the N900's port.