I just purchased a 64GB SDXC Card off Amazon.com, manufactured by Transcend, and fitted it into an SDHC CF adapter, and It WORKS! True, it comes formatted using the exFAT file system, and you need to insert it into a USB adapter, connect it to your computer, then use the "HP USB Disk Formatting Tool" to reformat it to FAT32, but after that little exercise, it works Perfectly. My device is, as always, a Dell Axim X51v, running WM6.1 LennySH's A07 Beta 3 version. My guess as to why this is, is that an SDXC card is basically just an SDHC card formatted with the exFAT file system. If you reformat it to FAT32, it will work on all manner of devices with no issues.
Cool then i think its time to take out my x51v, how is the write speed?
Did the hp tool complained about anything, and then you have a FAT32 64gb or close to it?