YMMV. Time, energy, compat*ability problems, unforseen issues which cost time debugging.

Again, I'm speaking for me -- there has to be a tangible real benefit and within networks even with 100 devices IPv4 does the job better than fine and better than IPv6 for some folks.

Not to mention its just plain easier to remember 4 octet sets of numbers running from machine to machine in an office than 6 or 8 or whatever.