I've never minded the wheel on the X1, mostly because it was my first iPod replacement and so incredibly inexpensive. If anything, the looseness of the AP100's buttons had me more concerned about longevity.
I don't find the buttons on my AP100 to be loose at all..they might loosen over time I don't know but I think Fiio could have done better with their scroll wheel. Apparently the scroll wheels are the same on the X1 and X3ii and they just feel flimsy to me and not very accurate when scrolling through lists of music. Shanling is about to release the M2..a smaller and less expensive version of the M3...looks very interesting...