So I just got home buying a 32GB Adata MicroSDHC class 10, UHS-I card. Then found time to read this thread...

.
...so it works at least..
...rather good even..
I will test the internal 4GB versus the 32GB Adata SDHC in Crystaldisk, what can only give me an impression, since I didn't open up my case yet.
32GB Adata MicroSDHC class 10, UHS-I card
versus 4GB Internal Kobo card
Sequential Read : 16.315 MB/s versus 16.302 MB/s
Sequential Write : 7.078 MB/s versus 6.546 MB/s
Random Read 512KB : 16.323 MB/s versus 16.313 MB/s
Random Write 512KB : 12.158 MB/s versus 14.810 MB/s
Random Read 4KB (QD=1) : 2.039 MB/s versus 2.039 MB/s
Random Write 4KB (QD=1) : 2.038 MB/s versus 2.037 MB/s
Random Read 4KB (QD=32) : 2.039 MB/s versus 1.585 MB/s
Random Write 4KB (QD=32) : 2.038 MB/s versus 2.038 MB/s
Test : 100 MB [30.1 GB)] (x9)
As my pdf's are typically 8-17MB the random read values of 512KB (200 reads of 512KB equals 100MB with an average speed op 16.3 MB/s) it seems it doesn't really matter whether I put a pdf-file on the internal of the external card.
I am quite honestly a bit surprised that the 32GB performs the same (in windows over USB) as the 4GB card!!
Would the earlier post imply you get a significant increase in speed in the Aura HD with a class 4 card the internal bay?