I'm having a LOT of fun with the X block using the author/designer Sharon Craig's template from the book. I was ready to make a kid quilt, so I chose to do a 9-block child size throw for charity. The colors in the inspiration piece ("jewel tones and neutrals" you said) are very similar to what I decided to use, but I went with a more juvenile "feel" since that one was what I interpreted as "grown up."
I have 5 blocks sewn so far.