Great place for trail running if you live in the area. If you are looking for solitude try the trails behind PIR. That trailhead can be accessed by the parking lot entrance to PIR just west of El Mirage road. The Technical Loop trail is about 5 miles long and the Long Loop trail is around 10 miles. No big climbs, just lots of rollers on mostly singletrack trails with a few sections of jeep trail thrown in.
For hiking I prefer the White Tanks or South Mountain, but for trail running EMRP is a hidden jewel. Very rarely do I ever run into more that a handful of people on any trail.