I see a few guys at each race on SS. They usually don't get there own class, but they have a blast all the same. I know a couple of dudes that have two bikes, one SS and one geared, they choose based on the course and how miserable they want to be.
I would think that the ENO hub would be wise since you can use any cross frame for the project, not a ton of SS cross rigs out there.
If your beer isn't Belgian you ain't racin' 'Cross!
I raced SS this year in my first year of doing CX and loved it. I had an IF Planet X built with track dropouts as I wanted it as my fixie and got a flip flop hub. Honestly, it was a great way to start the sport as it took shifting and drivetrain/weather out of the equation and gave me a very good gauge on my fitness. In NJ it was me and a 60yo as the only people. I raced C's and was usually top-10 with a few top 5's. One guy from Oregon said they have a full class out there and I saw that in SoCal, they had 20-30 SS guys each weekend. It is different and depending on course design, it is a better option. Try it, what have you got to lose?
That said, I am getting a geared CX bike for next year and will probably race 2x's per day; C's on the SS and B's or Master's on the geared bike. I just can't keep up with guys on flats b/c I'm geared to get over the hills. There's only so long I can hold a 130 cadence.
I saw someone on a Surly singelator and was happy with it. ENO should be fine too.