I haven't tried any trail running yet. It's been sort of wet here, and I want to try it in more like ideal conditions. I can see how a trail run could be a great alternative. Do you do much steep stuff as runs? The trail I hiked last week would be a great run, I think. It isn't steep, but it is a constant up hill. I've been conducting an informal poll: are specific trail running shoes necessary?
Define "steep". Typically my trail runs will be in the 600 - 1,200 ft of elevation gain range, depending on how long the run is and where I go. Did one that was a run/hike that was 2,500 of gain and that was kind of awful but felt amazing by the end. A constant mild grade sounds like it would be a great workout and will probably kill your quads. Which is the best, right? NO. At least I don't think they are, I run in hiking shoes or in running shoes depending on the grade and how comfortable I am with traction on the trail.