Great easy day hike - doing the primrose trail side loop (which takes you past Sandstone Falls) is worthwhile, though a little muddy, and takes the hike to an even 6 miles. Much of the hike is beauty barked or graveled, but some parts are pretty muddy (but nothing you can't handle in trail running shoes). There are little side trails that circumvent the worst of the mud if you look for them, and some pretty impressive bridges for a small pedestrian only hike. There are some cool remnants of mining operations along the trail, including an old coal mineshaft, and at the Red Town trailhead (can be the start/end or halfway point depending on where you start) you can find the ruins of the old Newcastle Hotel boiler room.
Definitely would recommend as a trail-running option, or an easy day hike (I did it after work, and it was perfect). 8/10