I use the faen and another race that was inspired by both the verrik and the alabast.
In my attempt to make every classe offer special abilities at least every three levels, I've merged the magister with the wizard.
I've modified the warmain a bit and it has become the Knight class. The Weapon Size Increase ability is restricted to use when charging or overrunning on horseback.
This Knight class, alongside with the unfettered, are used beside the Fighter. The Fighter is the general class, found everywhere; while other combattant classes like the Knight, the Unfettered, and the Clanwarden (renamed OA samurai) are found only in certain cultures -- human aristocracy for knights, dwarven nobility for clanwardens, people frequenting fencing schools in one specific country for unfettered...
I thought about using the greenbond and the totem warriors, but eventually decided not to. I'll keep the witch (but not all witches; I have nice variant witches I want to use); and I'm still undecided on the akashic -- if I use it, it'll be renamed mentat and its powers will be psionic based.
The biggest impact of AU, however, is on the magic system. I use the spells from the Player's Handbook, not from AU.
However, I was wanting to not use class-dependant spell lists. Having a sorcerer spell list, a wizard spell list, a bard spell list, an assassin spell list, a wu-jen spell list, and so on was, IMO, a bad idea. First, it makes the arcane/divine distinction irrelevant. Clerics and druids cast divine spells, wizards and bards cast arcane spells. Yet the bard and the cleric have spells in common that the wizard can't cast; and the wizard and the druid have spells in common that the cleric can't cast. What the smurf?
You see, in AU, classes don't have spell lists. They have spell access, determined through complexity of spells (simple, complex, exotic) and descriptors (for example, greenbonds get access to all spells with the Plant descriptor).
So, I decided to do the same. I've added even more descriptors than AU, and there are only four spell lists. Arcane, Divine, Nature, Psionic.
Classes now get descriptive spell access, rather than enumerative spell lists. For example, Bards cast arcane spells from the illusion, enchantment, and transmutation schools; as well as evocation spells with the [light] or [sonic] descriptors.
And that's it.