Homepage : PCSX
Still in BETA phase? Who cares if it works like this. USB joypads work like a charm (max 2 players), the app got a huge compatiblity list (link) for its early state of developement, plus it is free. Though the readme tells you a Sony Playstation BIOS was recommended for enjoying your games, the app allows you to play without. Since the legal situation regarding those BIOS files isnt fully clear to me, as it seems you are allowed to download and use them in case you own a "real" playstation, but still I am not sure about this and as a result I suggest you google for "SCPHBIOSES.zip".
Talking about software, the variety of games for the Playstation 1 is unbeaten untill today. Titles like UFO Enemy Unknown(link) show the Playstation´s ability not only to star in the field of action games but also in strategy games.
In OS X Tiger its possible that older games like the above mentioned mount 2 volumes when the game cd is insterted. As a result PCSX wont work on these games. To avoid this problem simply help yourself to Flarestrom 2 (link) , fire it up, throw in the game cd, only one volume will mount, quit FlareStorm and fire up PCSX again. I know this is a lame workaround but it works! In addition to that the ability to "prepare" game cds for PCSX seems to be all FlareStorm can do as it didnt work for me to play games.