Originally Posted by DNSB
I also found that the uSD card has quite a effect on the time it took to display the books stored there. There was a discussion together with some test results for various brands
Interesting stuff. I bet it matters how you format the SD card too. The Kobo will automount FAT, EXT2/3/4 and probably NTFS (and loads of others), and some formats are bound to be faster than others.
FYI, You don't have to remove the external SD when performing a factory reset - it won't be touched, but it will be rescanned when the Kobo reboots.