I bought this for using with micro-SD cards (obviously). I didn't need anything fancy. I just wanted something that was small and something that works. This fits the bill on both counts. I also didn't want to pay a fortune. So I passed over some that were more expensive or larger.
The only issue I've really had with this thing is that if you handle it a lot, the card will sort of lose contact with the adapter inside somehow and when you plug it into a USB port, you get nothing. It is not hard to make this happen either. I pulled this out of a USB port one day and put it back in about a minute later and it didn't show up as expected. I pulled it out again, pushed on the card to make sure it was in securely and then re-inserted the reader into the USB port and it showed up.
So it's not hard to get it to work again if it loses contact but obviously, it shouldn't do that when you're just gently handling it. When it does happen, it doesn't even feel like the card is even slightly lose so it obviously is a fault that happens with very little movement.
I did not buy this thing for the speed and haven't tested it. I don't need it to be really fast as I just dump relatively files that I need to take with me on it.
In conclusion, I can't really recommend this very highly. There are probably better options for not that much more money.