To reach the specified speed, you need to install a special driver. While under Windows XP this is very easy under Windows 7 we ran into some troubles. Our AMD890GX/SB850 test-system would not let install the driver because Windows said it's not digitally signed. So we had to force the System into the Test-Mode where unsigned drivers could be installed. Why it worked on our P55 system we can't say. Another problem is, the driver is only 32bits and no update to 64bit in sight. In the year 2010 with 64bit OSes around for five years it's not acceptable. Of course, it won't work with other OSes besides Windows.
Aside from that, the stick worked without flaws and there is virtually no speed difference between P55 and SB850. Of course without the drivers you get only 30MB/s read-and 20MB/s write speeds. The 16GB stick is the most price-sensitive one with a price of about €41,- while the 8GB costs only few bucks less and the 32GB and 64GB versions are accordingly more expensive. If you are lucky and have USB 3.0 ports, you can get even faster sticks such as the ADATA Nobility 32GB stick which only costs €6,- more and the 16GB version for only 30,-.