Remathilis
Legend
All I remember about PO was that they overhauled the psionics rules and in the process utterly ruined them. It was one of several changes that ruined our 2e Dark Sun campaign (since the new psionics rules were adopted after the Dark Sun Revised box came out).
Our group tried the following:
* Character-Point char-gen. Surprisingly, none of use abused this system too harshly, but we didn't go for outlandishly wild character either (our dwarven psionicist lacked infravision, but he justified it by his psionics affecting it). The big thing was most people traded followers for some minor perk. (Our fighter got the d12 HD, etc). So we only lucked out that nobody abused the system badly.
* Kits: PO kit system was great, but nobody used them for some reason. In our later 2e games, they replaced the Brown Book kits though.
* Proficiencies: Combat and Tactics introduced weapon mastery, an easier unarmed combat system, and a few weapon proficiency options (one of them gave non-single classed fighters a crippled specialization; which saw some use). This all hung around after.
* New Classes: A big like. The Crusader, Monk, and Shaman all slowly replaced specialty priests in some games, and the various specialist wizards were liked (shadow mage especially) but our group never liked specializing so mage was still the most popular class.
* Psionics: Never figured this one out. It was bad. We stuck to the Complete Psionics Handbook when applicable. (I believe the rules were built for Dark Sun, but put into PO first).
* Spell Points/Systems of Magic: Tried, and disliked. They ended up hard to do without a calculator or computer system (yay core-rules!) By the end, most of us were using the normal spells per day column anyway. (and giving a bonus spell for Int for Wizards). That said, some of the systems were cool and we attempted to try to convert them back to spell slots...
* Phase Initiative: OH MAH GAWDS. D&D combat could be slow; this dragged it down to a crawl. It lasted one session before going back to PHB initiative. Some of the grid combat lasted though, so we were not shocked by Attacks of Oppertunity in the 3e PHB.
* Critical Hits/Spell Criticals: Another Ones-and-Done. Again, dragged the game to a crawl. We used the default double-damage on a 20 rule.
* Additional Spell rules: Never used. Always forgot the existed.
* New Spells/Spell Lists: Mandatory. Cook wasn't thinking when some of those spells got assigned priest spheres, so PO went back and fixed spell access (stuff like giving druids, not clerics, access to reincarnate or giving priests with the healing sphere access to remove disease. So much common-sense fixes they were Cannon even in our "Core rules only" games).
Eventually, we condensed all our used PO stuff into like 60 pages of house rules in a binder (easy to do since the full text was on the Core Rules CD) that had the classes, kits, proficiencies, and spells from PO listed in it. Much of the other stuff went to dustbin. I could NOT imagine using character points, spell points, or phase initiative again (and the fact little of it saw the light beyond Dragon, a module, and Core Rules makes me think it wasn't all that well accepted.)