I love Opal yarn to knit socks. For one thing, it is bouncy! It just feels puffy and wonderful to knit with. No problem with splitting the yarns as I knit. It is also a yarn that has been around a LONG time and knitters who use it will tell you that socks knit with this yarn will last awhile!
Also, the colors are wonderful. Any and all colors!
And price - very reasonably priced. I think I paid around $15.00 USD the last time I bought it but I think it's even cheaper on Etsy (if you are willing to wait for your yarn as it travels from Lithuanian, which I am sometimes will to do). AND that is for a ball that is easily big enough to knit a pair of socks in most any size with some leftover. Opal for the WIN!