I loved my Montrail Streaks that I have worn for a few ultras, and I wanted to try something a little more protective without much additional weight. The new Hardrock looked like just the ticket, and that has proven to be a good conclusion.
The Hardrock is a little wider than the Streak, and most other shoes I run in. I figure I can live with it, because my feet get wider over the course of longer races to fill the shoe better by the end. I always replace the stock insoles with SofSoles cushion insoles right out of the box, and the extra room in the shoe made that an easy thing. It is no heavier than the Streak, as far as I can tell without weighing them both. After a couple of short trail runs in the Hardrocks, I figure they have marginally better traction than the Streaks, and better than the Brooks Cascadias I also use. Both the Streaks and Hardrocks cause no problem for road sections, though I am not tempted to road race either. They have a better heel-to-toe transition than a lot of the road shoes I have worn.
Anyhow, I decided to wear them for a trail ultra after only a few miles, despite knowing better. I am glad I did. Numerous stream crossings caused no issues, as the shoes drain well. There were places in the race where the extra traction was absolutely essential, so I was grateful to have it. Even wading through mud and muck proved the value of the shoes. Many shoes will collect mud, but Montrails in my experience shed mud well; so you don't have to stop to clean your shoes. One pair can work for the whole race, where some other shoes need to be changed after a few stream crossings.
Overall, I couldn't be happier with the new Hardrocks for trail running.