I didn't used to use an SD card until the firmware update that had the storage bug. Three resets in two days. Three times in two days, I had to wait for Calibre to copy across all my books.

Then it happened again a few days later.

Now, I don't have a huge collection of ebooks (just over 250), but it was a massive pain and a complete waste of time if I'd just used an SD card in the first place.

Generally, I do prefer using internal storage, but not for my KT. Never again. Even though I haven't had any problems since the storage bug was fixed, I'm keeping the SD card in there just in case. It's a class 10 8GB card, so I'm unlikely to run out of space for a while and loading books off the card feels marginally faster than off the internal memory (I'm probably imagining this, though).