I descended C twice. The first time coming off of Solar Slab, the second time coming off of Black Orpheus.
What I liked about "C" :
Immediate relief from cold, brutal winds if suffering on upper slabs. I was freezing and knocked down twice by the mean winds on the upper slabs and had to crawl on my hands and knees to gully(ouch).
Single rope descent.
One of the most beautiful gullies I've seen in Red Rock.
Fun downclimbing and scrambling in between short raps.
If moving fairly quick, can get down to Solar Slab terrace in less than an hour.
What I didn't care for:
The ratty rap anchors. Pretty much most of the rap webbing could use replacing.
You'd drown and/or get swept away if caught in the narrow, steep gully in a sudden rain storm.
The first time my partner, and I did the "C" gully, it had snow for quite a ways down (maybe 6" to one foot deep), a little bit of ice, and some small pools of water , but wasn't too bad. We just had to watch our footing more.
It's easier to locate the gully from atop Black Orpheus; Solar Slab a little trickier.
you havent heard of them for good reason- they're kind of epic in comparison to the standard options (rappelling the route, using the BO descent). Folks who are comfortable with Red Rock and its quirks may not find them to be that bad, but people who dont live here or frequent here often can easily find themselves hosed on these descents.
as for the anchors- i would not expect them to be any more than crappy old tat and old smc rings at best, as these descents are not used 1/10th as often as the ones noted above. if you choose this adventure, i'd bring at least 30', if not more, of webbing and cord to shore up the rap stations.