Some mud and rocks do get into the downtube but just as they got in they fall right out. The production bikes have a conical shaped cap at the bottom of the downtube which serves to funnel the debrie out even better. The heading picture on the main blog page is from our first ride in St. George where we were in some of the thickest and sickest mud I've seen. It didn't attract more mud than any other bike I've ridden. And it was out before the ride was over.
How does it ride?
It rides like most hardtails. The Isotruss is stiffer than I would have expected. The climbing with the Arantix is phenomenal! The head tube angle is rather sharp and therefore very tight and quick on turning. On the other hand for the same reason I have found it to be a bit more unstable up front and tended to wash out on me until I got used to it. No problem now.
Is it strong?
Boy is it strong! I have taken quite a few hard drops and several spills and endos and even after 600 miles of hard riding and racing it's integrity is not phased. I even have one of the small isotruss triangles broken on the down tube and the integrity of the frame is intact (about 200 miles riden with it broken).
Remember; the rate limiting component in cycling is the engine. Ride on.....