Sequential
---------
Write uncached 12:45 7.65 MB / sec [4K blocks]
Write uncached 13.84 7.83 MB / sec [256K blocks]
Uncached Read 12:17 3:56 MB / sec [4K blocks]
Read uncached 36.56 18:37 MB / sec [256K blocks]
Random
-------
Write uncached 9.71 1:03 MB / sec [4K blocks]
Write uncached 20:34 6:51 MB / sec [256K blocks]
Read uncached 405.98 2.88 MB / sec [4K blocks]
Read uncached 98.45 18:27 MB / sec [256K blocks]
The letter again on OS X SL, a 22.4 MB file takes 2 seconds to read 1 second. For me perfectly adequate.
Comparing these values with those in this test, [...] so you can quickly even an opinion on price and performance form.
By the way: with an adapter from Samsung achieved the card slightly better transfer rates, especially in writing.