I got the Kingston 16GB class 10 and it's hanging right around 4.9MB/s write speed as well.

Having tested two class 10s, I believe the fault may lie with the Gumstix itself.

Nevertheless, 4.5MB/s is good enough for my application - if it is consistent even with other system loads.

For reference:
the network transfer rate is about 10MB/s (100mb/s), but less using ssh (encryption slows the transfer).

AJ ONeal

On Thu, Sep 2, 2010 at 6:25 PM, AJ ONeal <coolaj86@gmail.com> wrote:
I'm testing out various brands and classes of microSDHC to see which actually perform as they should and whether the microSDHC or the gumstix data bus is my write speed bottleneck.

http://fastr.github.com/articles/testing-file-write-speeds.html

So far I would recommend Kingston. It's more expensive, but it performs well. I should have a class 10 of theirs soon to test against.

AJ ONeal