I love mystery quilts! Normally I am a control freak so I like how they put me out of my comfort zone. i have done at least 4 of Bonnie Hunter's,some I liked, others not so much. My favorite kind are the ones where you come with much of the cutting done and you get it done ( or mostly done) by the end of the workshop. We have done several at our quilting Bees meeting in Tupper Lake, NY and I did one at the Vermont Quilt Festive. In fact I even taught one last year. What fun to watch everyone guess and then change their minds as to what it would be.
The main draw back is knowing what fabric to choose. When I taught , I offered to help them select their fabric to increase their chances of liking the finished product. Bonnie Hunter does that with her paint chip idea.
Relax and just go for it!