Picked up the Kingston class 4 32gb microSD card from Newegg and tried it in the EVO, initially it would not recognize the card until I formatted it. It was already FAT32 but I formatted FAT32, 32k, and it then recognized the card.
I then copied everything over from my Sandisk 16gb card and did some speed tests with Crystaldiskmark, here are the results:
16GB Class 2 Sandisk Micro SD Card
Amazon.com: SanDisk 16 GB Class 2 microSDHC Flash Memory Card SDSDQ-016G (Bulk Packaging): Electronics
SanDisk 16 GB Class 2 microSDHC Flash Memory Card SDSDQ-016G (Bulk Packaging)
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CrystalDiskMark 3.0 x64 (C) 2007-2010 hiyohiyo
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Sequential Read : 20.840 MB/s
Sequential Write : 7.098 MB/s
Random Read 512KB : 20.467 MB/s
Random Write 512KB : 0.994 MB/s
Test : 100 MB [H: 74.0% (11.0/14.8 GB)] (x5)
Date : 2010/11/04 12:49:06
OS : Windows 7 Home Premium Edition [6.1 Build 7600] (x64)
32 gb Class 4 Kingston Micro SD card
Newegg.com - Kingston 32GB Micro SDHC Flash Card with MicroSD Reader Gen 2 Model MRG2+SDC4/32GB
Kingston 32GB Micro SDHC Flash Card with MicroSD Reader Gen 2 Model MRG2+SDC4/32GB
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CrystalDiskMark 3.0 x64 (C) 2007-2010 hiyohiyo
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Sequential Read : 18.437 MB/s
Sequential Write : 4.636 MB/s
Random Read 512KB : 17.340 MB/s
Random Write 512KB : 0.656 MB/s
Test : 100 MB [H: 36.6% (10.9/29.9 GB)] (x5)
Date : 2010/11/04 12:55:43
OS : Windows 7 Home Premium Edition [6.1 Build 7600] (x64)
So you can see the speed difference between a Sandisk Class 2 and a Kingston class 4, the Sandisk did much better than the Kingston, but since I got the Kingston for $86, I don't really care, it is working fine, and the USB adapter is pretty nice too.