The meenova seems to be slow even with a class10 microSD card. I haven't measured the speed but the hit might be half the speed of internal memory. It's a little awkward to hold in the hand and because of the orientation of the usb port on the phone, the "back" side faces up. These are all small issues (except the speed, that's pretty noticeable) and I don't regret buying it, but I would definitely prefer having as much space on the internal drive as possible
edit: tried an app called SD Tools to measure the speed.
Internal: write: ~130MB/s; read ~200MB/s
Meenova: write: 40-80MB/s; read ~220MB/s
If you can get apps to install there, speed might not be a problem, just the inconvenience of having the adapter in the way