I did go ahead and get the Noro Silk Garden for my arm warmers, because there really wasn't an alternative. The next closest option was 30% wool. Interestingly my LYS does have a self-patterning non-wool yarn in worsted weight, but that would have been too busy for my project.
BTW, my project:
Honestly, IMHO, this pattern is not all it could be. First, the reverse stockinette background is too wide. If I were designing it, I'd leave one purl stitch on each side only, not two. That's why I don't like ones done in solid colors. The Noro gradient helps add some interest; without it, there's just a huge expanse of ass-ugly reverse stockinette.
The designer also does not consistently twist her traveling stitches. I've changed that as I knit.
What makes me very dubious, though, is that this has the shortest thumb gusset in the world. Only 7 rows. Having made a mitten or two in my time, that seems waaaay too short. Normally I would work a plain row between each increase row to get more length. I'm sure I'm reading the pattern correctly, though, because I checked. Then I checked again. Then I checked a third time. Then I squinted at the sample photo and counted rows. Then I flipped to the other sample photo and counted rows again. Then I went to Ravelry and counted rows on some of those photos. Then just for good measure I double-checked the errata, and then clicked some more Ravelry photos. Because it really doesn't seem right.
I am really quite convinced that the pattern intentionally has the shortest thumb gusset in the world. I'm not convinced that's going to be comfortable, however. Actually, I'm wishing I'd put in a lifeline before starting the gusset, and I may frog back anyway and add the increase rounds. These are going to be so long on my fingers that I've got room to do it, although unfortunately it'll make the cuff even longer. Gosh, I hope this yarn'll frog. It's got an awful lot of mohair in it.