This is a very nice yarn store with a pretty large selection. I've picked up the tradition of buying yarn when traveling/meeting a milestone, so I bought some yarn from Gail Knits right before running the Las Vegas Marathon (my first marathon!). The selection is carefully curated - don't expect to find every color from every yarn! (I learned this when I returned last month to buy a color to coordinate with the yarn I bought in December -- the colorway I wanted wasn't available at Gail's.)
The ladies who work here are very friendly, and there seems to be a nice group of local knitters who hang out. It would be a great LYS (better than the ones I have in my hometown!), but there are certainly bigger and more impressive yarn stores in larger cities. In other words, for tourists to Vegas it's definitely worth the drive away from your usual touristy area...unless your LYS is the best of the best!