I love working with semi solid yarns - they're the perfect addition when you want to add a pop of colour to a project, they work well with variegated or speckled skeins, they can help tone down a project that's too bright, you can hold them doubled with other yarns in a blanket or jumper, and they're perfect for socks whether as heels and toes or in full socks with a lace/cabled design.  The possibilities are endless.  I have a range of semi solid colourways and I'm always adding to the collection!