This is a very nice paved trail. If you're looking for a real hike, this is not the place, but it's a lovely place to take a long walk with dogs or strollers. There's plenty of lake views and good amount of wildlife to take in. A fun place to take the whole family!
This is not a difficult trail by ANY means; it's not even a moderate one. this is a very flat, easy, mostly-paved path that is well maintained. There are cyclists, walkers, runners, and children on the trail. I ran this easily and kept a steady pace, along the river and through some wooded areas. Extremely easy.
I'm not sure why this trail is rated as difficult, as its pretty flat and unremarkable for hiking. There is a paved pathway around most of the lake and a lot of very small trail segments in a wooded area - with no blazes or trail markings at all. Its a great community park, but for hiking its nothing I'd go out of my way to hike again. I'm not even sure why its in All Trails - its a great county park but not really a hiking destination.
The exceptionally well-maintained "Mercer Meadows" complex is a real boon in central New Jersey, othewise not famous for its extended stretches of open space. The area has been expanded, with several ways into it other than the original Mercer County Park entrance near the lake.