Montrail Vitesse!
I have found that the women's Montrail Vitesse (a men's model is also availbable) are ideal for trail running. They are supportive and rugged. I recommend using a light sock and wearing the same size shoe that one wears for other sneakers. The light-weight sock quickly dries and thereby doesn't increase the risk of blisters. These shoes did not require a break in period as they were as comfortable as slippers, yet supportive as low-rise hikers (no ankle support).
The Vitesse's manmade uppers remain unscathed after many, many miles of rugged trails and intense bushwhacks, while a friend of mine wore another brand that were totally shredded after the first use. The stitching is incredibly strong.
The Vitesse have small mesh ports that are breathable to provide the necessary ventilation for foot heat as well as providing drainage when the trails are wet! I do not recommend shoes utilizing Gortex or other "breathable" materials since this is not as durable and the water/mud usually comes over the top. Gortex gators are quite nice to reduce the amount of trail debris that collects in your shoes.
The Vitesse soles are not the best for situations that require aggressive grip, so I usually end up carrying my rock shoes if the route includes a steep slide climb.
The attached tongue system keeps the tongue from sliding from one side to the other and greatly adds to the comfort of these shoes; and the laces are incredibly durable as well as non-untieing (humph! I wonder if that is in the shoemaker's vocabulary?!
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Happy hiking and trailrunning!
Inge