Excerpt: For the price I paid for 10 of them, I am fairly happy. Each came with an adapter, which is nice. I think one or two of the adapters became unreliable. This may be the cause of someone's grief. I have 10 so I swap adapters when I find the card is unreadable and narrowed down to two bad adapters. I've used these on my arduino and raspberry pi projects and for file storage.
Pros: Easy To Use, Fast Enough On Arduino, Reliable Performance