Switching to Legacy with GEDCOM will not transfer the Detail A and B fields. So if you have used these fields you will have to move this information by hand.
Maybe the Legacy people could offer to make their program to accept the Event 1.x UFT GEDCOM.
If you are a user who prints Family Journals as a main report will find Legacy will not make sentences of event other than the basic BMDB information. The balance of the events are just a listing of data.
The TMG upgrade 4.0a will be interesting to see. As announced it will use roles, I hope like UFT does.