Q: What's the largest supported card?
A: I've tested 16GB, and it works, anything larger will too *
Q: Besides this driver what do I need to use big cards
A: On TX and LideDrive - nothing.* On all other devices to use cards 8GB+ you need a FAT32 driver.*
Q: How fast is it?
A: Currently the driver is significantly faster than the stock driver for multi-block writes, but until I release my own FAT32 implementation you're unlikely to see much increase in speed since palm's version of FAT32 rarely uses multi-block writes, for some reason.
*: PalmOS cannot report free or total space of a device over 4GB. This is an architectural and an API limit. I am releasing a hack that would help legacy applications overcome it in at least some way, while at the same time I will release a more modern api and encourage all software developers to use it.