I've been trying for some time now to figure out library update problems and other X3 issues. Here are some (perhaps useful) experiences:
1) If you try to add too many new tracks at once during a library update, the X3 seems to not do anything to the library file and does not give you any error messages. Using the same exact files, but adding the files (to the SD) in groups of roughly 1000 and updating each time, it works fine. I can now use the library for my 7000 audio files. (Note: I was using a 64gb SD formatted with NTSF 4k blks.)
2) Yes I had the same tag version issues other threads ( http://www.head-fi.org/t/715238/x3-library-hack-super-fast-library-update-proper-tag-id3-v2-playlist-support ) have talked about and are trying to resolve (thank you!).
3) A couple of times I somehow corrupted the files on the embedded drive. WIN7's "scan & fix" worked fine, but one can also format the embedded drive (I used FAT32 for that) with no ill effects.
So currently, if you want to use the library categories and you want to be able to swap SD cards, it can't be done with large numbers of tracks. (See #1 above) If the FW allowed for specifying the location of the library to be on the external (SD) drive, then the swap of SD drives would be more useful because you wouldn't even have to do an update. (If you're changing X3 units then you might due to the embedded drive, but normally you don't have too many files there to be a problem.)
I should mention that the library update time is not too bad when adding a few new files to an otherwise large library file (around 2.5 minutes). (Hey! all is relative!)
Really do love the sound though and, sadly, Apple is giving away the portable audiophile market.
Edited by BradleyJH - 6/3/14 at 7:25am