The creatures do not play a central role in Brust's works -- they have one major appearance in his multi-book Vlad Taltos series (so far), which is short enough to offer here, with thanks to Nexx for the typing. In this passage, the hero, Vlad, and his mentor/employer, Morrolan, are on a quest to visit the place where the gods live. Vlad is keeping an eye out for dangers by watching through the eyes of his wise-cracking familiar, Loiosh.
There were these beings, maybe two dozen of them, and I've never seen anyone or anything run so fast. They had four legs and from the waist down appeared to be feline, smaller than the dzur, perhaps the size of the tiassa but without wings. From the waist up they appeared human. They carried spears.
"I guess so, boss. I hadn't known they were real."
"Nor had I. Interesting."
"I think they're heading toward us."
I broke the connection, and by now I could see them with my own eyes, as a gradually resolving blur in the distance. Verra, but they were fast. I noted that Morrolan had not touched his sword, and I took some comfort from that. I began to hear them, then; a very low rumble that made me realize I ought to have heard them some time ago. They were awfully quiet for their size.
They suddenly stopped before us. The butt ends of their spears rested on the ground as they looked at us through human faces with expressions of mild curiosity. The spears had worked metal heads, which I decided was significant. I had the impression that they ran just because they wanted to. None of them were breathing hard. They stared at us, unblinking, like cats. They wore no clothing, but many of them carried pouches, tied around their backs and hanging down the sides. The muscles around their back legs were impressive as hell.
I said, "So what else do you do for fun?"
Morrolan turned and glared at me. The cat-centaur who was at their head, and who was emphatically female, looked at me and smiled a little. "Chase things," she said. She spoke Dragaeran without any trace of accent.
Loiosh landed on my shoulder, and the leader's eyes widened. I said, "My name is Vlad Taltos."
Morrolan said, "I am Morrolan."
She said, "I am called Mist."
A cat-centaur with red eyes said, "That's because when she throws her spear--"
"Shut up, Brandy." There was some laughter, which included Loiosh, though only I was aware of that.
Mist said, "The jhereg on your shoulder -- he is your friend?"
I said, "Yeah."
"Jhereg feed on dead cat-centaurs."
I said, "Dead men, too," which seemed to satisfy her.
She said "What brings you to the Forever Plains?"
Morrolan said, "We journey to Deathgate Falls," and the entire collection of cat-centaurs took a step back from us. I stooped down and picked and ate a strawberry, waiting.
After a moment, Mist said, "I assume you have good reason."
Morrolan started to answer, but another cat-centaur said, "No, they're just out on a lark."
Mist said, "Keep still, Birch."
I said, "Say, are those real spears?"
Morrolan said, "Shut up, Vlad."
Loiosh seemed about to have hysterics. Some of the cat-centaurs appeared to be in the same situation. Me, too. Morrolan and Mist caught each other's eyes and shook their heads, sadly.
Mist said, "If you wait here, we're following a very large wild kethna. When we bring it down, we'll share it with you."
"We shall get a fire going," said Morrolan. Then, "Um, you DO cook your meat, do you not?"
Brandy said, "No, we prefer to let the raw, fresh blood of our kill drip down our --"
"Shut up, Brandy," said Mist. "Yes, a fire would be nice."
"See you soon, then," said Morrolan.
"Quite soon, I expect," said Mist, and they turned and sped off the way they'd come.
In the socializing that followed, Vlad taught them to gamble (with what I think is a dice game). And he figured out that the creatures reveal their emotions with their tails: "I learned to know when I was pushing one too far by watching the tail."
There are a couple more scenes with cat-centaurs in that chapter, and elsewhere Vlad hears of or encounters the cat-centaur god, Kelchor. But that's pretty much it. Naturally, I wondered how it was that wemics ended up in the Vlad Taltos books, so I wrote to the author to ask.
I also had the nerve to ask if his cat-centaurs were metaphors, an idea I got from Bradford Holden, and Brust wrote back, "Anything can be a metaphor, and usually is. But spelling it out takes all the fun out. :-)"