I've run 2 of the races put on by Pretzel City, the Dirty Bird back on Thanksgiving and the Ugly Mudder at the end of February. Both were a hoot and great runs for me. I'm not sure what course he's set up for your Ugly Mudder, but I'll bet it will be a challenge. I wore my VFF's for both races and was glad I had them - the rocks were kinda wicked, and I just would have had to slow down way too much to traverse them. Even the VFF's elicited some "Wow! Hard core!sort of comments from the regularly shod.
I just ran the St. Lukes 1/2 Marathon in Allentown yesterday and don't feel like a trail race would make much sense at this point. I will be with you in spirit, though.
Be sure to post your results.