I think the only thing X3 is missing for me to be perfect, is manual sorting of the images within a gallery. Like X2 had. We do have random, desc, and asc, but it would definitely need a manual option.
Sometimes you just don't want an image to display next so a similar one in your portfolio. An manually move it is easier than having to rename the file so it moves in the sorting.
Might be a bit late for Release Candidate but I'm hoping it find it's way to an upcoming update!
Thanks.