I've flown at Marfa at those Dick Johnson sponsored spring wave camps.
I might go to a OLC camp there but I would not go to a competition, I found it to be too rough and unlandable for my taste, I'm a wuss and I'm spoiled flying Parowan Nephi where there are lots of airports and Ag fields in case things go south. Coming back to Marfa from the Davis Mountains one day in my Ka6CR in a gale I couldn't make the airport and landed on the highway, no steel stakes where I landed, but not the best as there was some traffic.
Going to Marfa to see the "Marfa Lights" was worth it thou, goggle those things they are really something to see.