"Good, cheap card but slow transfers"

I purchased this card for use in a Microsoft Surface Pro tablet -- for that, it works great. 64GB is a nice capacity, card was cheap and it works just fine.The problem, however, was in transfer speed. It's rated at "up to" 30MB/sec which I guess is true.. but mine has never reached anywhere close to that. Using 3 different readers (the Surface Pro itself, a higher-end desktop PC with built-in MicroSD reader and an external USB 3.0 MicroSD reader.. in all, it maxed out around 10-12MB/sec (and on multiple smaller files it maxed out closer to about 5MB/sec total). I know it's not the card readers as I have been able to reach speeds of 90MB/sec with other/faster cards.The card itself DOES work fine. For that I give it 5 stars. The price is great for the size, for that I give it 5 stars. The transfer speeds are just disappointing though.. taking 5 minutes to transfer an iTunes movie file is a long time.. it'll take hours to fill the full card.. If you only load data once, it's not so bad, but if you're always adding/deleting/moving data, it's slow and will get annoying quickly!