This thing is, quite simply, like greased lightning and probably quicker than the proverbial off a shovel.
It almost makes the 6 (RAW) shot buffer on an EOS 7D a thing of the past as it seems to increase to a more usable 9-10 shots before it slows down - and even when it does slow down, it still seems to be usable. On JPEG only, the buffer is now effectively endless although I'm not going to take several hundred shots at 8fps just to find out for sure!
Though I'm more than happy with the performance increase it's brought to the 7D, where it really is a game-changer is with a ridiculously quick card reader. I bought a Lexar Professional USB 3.0 Dual Slot Reader
to go with it (although obviously you'd also need a USB 3.0 port to plug it into)...
Downloading ~16GB from a CF card used to take between 10 mins (Sandisk Extreme III 30MB/s) and 25 mins (Kingston Elite Pro 133x) on a non-UDMA Firewire 400 card reader. It now takes just 3 minutes and downloads at a fairly constant 80MB/s. That's close enough to the rated 90MB/s for me!
It's not exactly a cheap buy but with the right gear, it's a seriously quick card and worth every penny.