I have it and like it a lot. I think you will like it. It has much of the same origins as the free program ChessX. I post the most recent builds of ChessX for the Macintosh ( and occasionally windows ) to www.box.com/chessx. The official chessX site is http://chessx.sourceforge.net. In some ways they are very similar programs. Hiarcs has a very nice opening explorer, and you can play games against it. ChessX is more of just a PGN database program. I suggest trying ChessX and then if you want to pay for HIARCS Chess Explorer go ahead.
The Opening Explorer in HIARCS will be invaluable in studying your openings. If you download ChessX you will also want to download Stockfish and install it into ChessX so you can analyze positions. Both ChessX and HIARCS are great for playing over games and studying them.
I have seen a you tube video of this chess program for the mac and it looks really nice...
http://www.youtube.com/watch?v=MtBdRjtrBDU
I want to use it to enter my games and analyse them and play through some games of great players. I would like to study my openings as well. Does anyone have experience with this mac chess program?