This seems to evolve into a SD card benchmark thread... So, these are the cards we (will) have:
I want to buy this card if Class 10 SD cards Work properly:
That would be a "ICIDU 8GB, Class10, 20MB/s"
Small test on the above mentioned card "Sandisk Ultra 15MB/s SDHC Card 8GB":
Writing speed: 9.82 MB/s
Reading speed: 18.88 MB/s
The Foundation chaps report that SanDisk Ultra series cards work fine. I unearthed a SanDisk Ultra from one of my cameras, which is among the 50MHz, 4-bit interfaced examples.
This should hopefully be corrected when the cards I have ordered finally arrive, as they include a SanDisk Extreme series card which claims a UHS-1 performance rating
FWIW i have a 8gb samsung class10 micro SD waiting to test as soon as my pi arrives as well as a 8gb class 4 as a backup.
I've just got hold of Class 10 4GB cards from both SanDisk (Extreme series) and Transcend (black label).
After exploring the nether regions of my friendly local computer megahyperstore, I now have an extra selection of SD (and MicroSD) cards from two additional vendors (Kingston and Verbatim) to play with. Most of them are Class 10s.
Now, i'm gonna order a Panasonic 8 GB SDHC Gold (UHS-1 / Class 10). They claim it can read at 90MB/s, and i'd guess the read speed is very important for our intended use as primary linux filesystem. Shall we use f3write to compare results once the r-pi arrives?