I spent a bit of time researching looking for a suitable product and couldn't find a definitive answer, so I am hoping this review will help anyone else in a similar situation.
I bought this memory stick/flash drive specifically for use in my car. On the E90 3 series with the USB audio, there is a USB slot under the central armrest into which you can plug your flash drive or the offical ipod adapter. The only problem with the location of the socket is that it doesn't leave much headroom when you shut the armrest, therefore a normal sized flash drive would be snapped off. So to use a normal flash drive you'd need to have an extension cable, which would do the job but would leave the flash drive flapping around in the storage compartment, probably rattling & getting in the way of whatever else you've got in there. This tiny flash drive fits snugly in the socket, it won't catch on anything else & so won't get snapped off.
Positive Points:
Comes formatted in FAT32 which is recognised straight away by BMW audio and so you just drag & drop your files and you are off, with your albums appearing straight away on the car's audio screen or idrive if you have it.
Size & design makes for a flush fit which can be forgotten about once installed. It really is remarkably small!
Negative Points:
Very small (obviously) so very easy to lose (it does have a small clip for attaching a cord) so if you want a drive to carry around and swap from one PC to another on a regular basis, then just go for a standard sized drive.
Fits very securely into a USB slot, which is great when you want to leave it in place (in a PC or a car) but the small size doesn't give much purchase when trying to remove it from the slot, so be prepared for sore fingers - at least on the first few uses!
Conclusion: If you are looking for a fit & forget storage solution for your car audio or laptop then I would not hesitate to recommend this. It definitely works with BMW and will probably work just as well with other systems that have a USB facility, just check the manual first!