Sin is a warmish champange shade, a great "My lid but better" type of color that makes it a fabulous base for pretty much any nude look for my NC15 lids. I find that shadows, including those from Linnaeus Cosmetics and other loose shadows, last all day without creasing or fading when worn over Sin. Because it's a nude-type color, it doesn't compete under neutral eyeshadows.
Urban Decay was right to include "Glide on" in the name of this product - they really do glide on to the skin. I found the NYX version to be a little rough on the skin (which can be especially annoying since my eyelids, like yours, do not appreciate being tugged on or scratched). Both Sin and Rehab apply very smoothly. I don't find these to be especially blendable, though. That may be why I like Sin as much as I do - I don't have to blend it, because it's ultimately going to be covered by whatever eyeshadow I'll be wearing that day. I can wear Sin over UDPP alone, but it does tend to crease a bit on it's own (that's after a 12-hour stint on my lids, though).
I always start with UDPP on my lids. I did try to skip that step, and was not surprised that my eye of the day was a little sad looking by the end of the day. I doubt these pencils can withstand oily lids alone. Not much really can, in my experience, so I don't hold it against this product.
Overall, I'm really impressed with Sin. It's been incorporated into my daily regimen because it's so easy to use and works beyond my expectations.