There's always the scanning part - just what color balance etc, and even the scanner software gives different results. A royal pain if you ask me.
To illustrate, one wintery dawn I went to Sandy Hook on the Jersey Shore with my K100D, a Yashica Mat 124G loaded with Velvia, (and my Ansco Shur Shot box camera with Fuji 160S, and ... a Fujica St605 plus a couple of Takumars). Too much gear, I don't like going with so much. But there were things I wanted to test out.
I never did get a scan I'm happy with, but then seems like MF in general I have this problem with.
Some samples:
Velvia, Yashica Mat, last scan w/VueScan
K100D, DA 16-45
Velvia, Yashica Mat, earlier scan w/VueScan
Velvia, Yashica Mat, Epson scan