Quick benchmark using CrystalMark 32bit on Dell M1330 Core2Duo Laptop, 5 repts 500MB:
Sep read:13.82MB/s write:12.71MB/s
512K random read:13.54MB/s write:1.28MB/s
4k random: read:3.695MB/s write:0.026MB/s
But compare to an old 1Gb micro sd card I used in my satnav:
Sep read:13.61MB/s write:7.218MB/s
512K random read:13.51MB/s write:2.341MB/s
4k random: read:5.746MB/s write:0.025MB/s
The play.com 16Gb Class 10 sd card do not performance so impressively consider its class 10 rating and the "up to 23MB/s" claimed performance.
I guess the max seq read/write performance maybe limited by the card reader on my laptop.