we are fortunate in that all of our users are in Custom Profiles, so we are "safe" in that respect. We have begun to undertake the work we need to do to make the switch, but there is a good amount of work yet to be done. It would be untenable to support users switching back and forth given the number of users we have.

Pieces we know need further work so far include dated exchange rates (unsupported in LEx or Classic), Custom Objects we have built (design decisions), and other items like the dated exchange rates that we may run into and find we "thought" were working but in fact are not.