Definitively YES. Nothing that extreme as a marathon, but I did a couple of 10-15+ km walks in the Sprints (the longest being approximately the length of a half-marathon, and I am looking forward to more) and greatly enjoyed the experience. Just watch out for interesting surfaces :-)
I walk sockless; may be the answer to your tightness problem?
Unfortunately no, sockless works for a little while then I get really tender spots under my big toes and eventually raw spots all over the bottom edge of my heels...which is weird considering how tight the front of them fits. I think I just need to admit that my 'stubby toed wide as canoe paddles' feet aren't made for VFFs and start working on full time barefootin'!