Here's what I found from the site. I guess I should have checked it earlier:
[Will Reunion import my data from another genealogy program? Yes, if your program will export a Gedcom file (it probably will).
Gedcom is a file format devised by the LDS Church which has become the defacto standard for exchanging genealogy information between different programs and different platforms.
The "completeness" of your data transfer will depend partly on the fields used in your other genealogy software. For example, if you're using PAF and you have recorded basic data such as names, birth/death/burial/marriage dates and places, notes, etc., your data should transfer fine.
However, there have been different versions of the Gedcom standard along the way (current is 5.5), and the Gedcom standard is, unfortunately, interpreted in different ways by different developers. In general, the more complex your current program is, the less likely your chances of a complete data transfer. Items like pictures, video, and sound will not transfer.
In Reunion, we have made every effort to interpret the various revisions and renditions of Gedcom files exported by other programs.]
TAKE NOTE, however ... that not ALL of your information will transfer via Gedcom. Good luck with your MAC! :)