Yeah, but these cards can run any filesystem you want. Linux's ext2 filesystem is reliable and even supported in Windows if you get the ext2 IFS driver.

Normally "mkfs.ext2 /dev/mmc1k1p1" would make the filesystem on a fresh card, but to make it compatible with the Windows driver you need different inode sizes:

mkfs.ext2 -i 128 /dev/mmc1k1p1

According to Wikipedia, for the short term, SDHC and SDXC cards will be compatible, but plans are afoot to make new SDXC cards support a 2.4GB/s data rate. These newer cards may be incompatible with SDHC.