I bought two of these a while back. They work adequately. I've used CF, SD and other card with no problems. Sometimes it can be a bit of guesswork which slot and which way around the card should go, but certainly for Compact Flash it is tabbed appropriately.
Good value for money and all that, but ... the socket for the USB cable is only soldered to the circuit board and quite wobbly. It stopped working after not an unreasonable amount of use - on inspection it was clear that the wires holding the socket had snapped. I'm normally gentle and look after my stuff, so I was surprised that this happened. If you're going to leave it plugged in and not dangle it by the cable (which is all but impossible!) then this little device might serve you a long time.
I'm about to buy another and it probably won't be one of these.