The best compact flash cards are 1000x (150MB/s).
USB 2.0 real-world max speed is approx. 30-40 MB/s
Firewire 800 real-world max speed is approx. 70-80 MB/s
USB 3.0 real-life world max speed is approx. 300-400 MB/s
Thunderbolt 1 real world speed is approx 1 GB/s
For still photography I don't think even a USB 2.0 reader can be a bottleneck of my import workflow. What I normally do is import pictures in Lightroom, generate 1:1 and smart previews and apply a preset and then go one by one and edit them. The image operations are far slower than copying pictures from the card reader. Copying can continue on background, so I can start working on images while they are still being copied. Thus I have no problem copying images from card even at USB 2.0 speed.
I think having a fast card reader is far more important for video users that for still photographers.