I bought these for Tough Mudder events, rather than trail running. I found that, compared to my team mates who were still in standard running shoes, I was able to run up and down muddy slopes with far greater confidence and far less energy expended, all down to the excellent grip on the soles. Regarding fit, they weren't as comfortable as my usual runners, but mainly because I hadn't been able to break them in as well as I'd like. Living in central London, there aren't that many off road paths to run on and I didn't want to wear down the grip running too much on pavements.
Overall - an excellent shoe for mud running!