Mir was very important that the stick is as small as possible, so you do not accidentally bump it and may break the stick. Since the stick but not even protrude a centimeter, there is no such danger. Just awesome. The stick looks like he would to the car radio to include (as well as black / red held, like the Pioneer DEH-4400BT).
To write speed I can tell from practice, it took 40 minutes approximately 2,000 MP3 files, which are a total of 10.8 GB in size to transfer from my computer to the stick. Whether this is a particularly fast or slow is something I honestly do not care, because I now my entire music collection on the stick (and thus on the car radio) have, and I will not change it much. It is of course now and then one or the other song (mp3 file) added, but what then takes a few seconds.
To read speed I can say that the stick is immediately read on the car radio and the songs change is at least as fast as CD. So immaculate.
There were a few files from Sandisk stored on it, these I simply deleted and the stick for safety's sake again formatted (FAT32). The stick has a mini-LED lamp, the only faintly flashes (so it does not disturb while driving because the car radio is anyway much more brightly lit).
All in all, just buy it. For questions, I am happy to help.