Since I got my 16 GB USB memory stick, which is a quite huge storage amount, I got the idea to make the best out of it and do a performance test.
Many disc accesses are usually done with a Virtual Machine, so I put a blank Parallels Windows XP virtual machine image to the stick, hoping the speed would be fantastic.
But, the hope still remains a hope. The speed is just OK, and absolutely not faster than directly starting from a harddisk. The USB probing sais 480Mb/sec which is a maximum of 6 MB per second, but the average speed I could measure in fact is 5.2 MB per second.
That is absolutely too slow and the conclusion for me is, that flash memory is only really fast if it will provided over the S-ATA port.