Ok - so I went and bought the Synchrotech ExpressCard to PCI-e reader -
PCI Express to ExpressCard 34|54 Slot Drive Read-Writer Front, Synchrotech
I got it yesterday and installed it without problems. It is very well buildt and professional in every way. The reader makes a beep noise when inserting and removing cards and it is very easy to rescan the reader when swapping cards using "find new hardware" in the Windows device manager.
I've made a shortcut to the device manager on my desktop so all it takes is a double click and a right click to find the new card. It's too bad Apple users don't have this possibility. Having to reboot would be a deal breaker for me.
Now, when it comes to speed I am more than satisfied! The bottle neck seems to be my harddrive. Windows is reporting transfer speeds of about 110-120 MB/s. That's about the same speed my harddrive can write at.
Copying a full 16 GB SxS card took exactly three minutes!
If you are on windows - go for it! (I am using Windows 7 - 64 bits)