I hiked about half of the Plantation Trail over the weekend. For birding, it was amazing. I saw about 6 different warbler species included several Black Throated Blues, a Blackburnian, and several Canada Warblers.
Unfortunately, the mountain biking crowd, of which I am a part of, is tearing the heck out of the trail. The weekend was fairly dry and yet huge sections of the trail consist of nothing but gear deep mud pits. Because of the Laurel and rhododendrons, it's nearly impossible to hike or cycle around these eroded sections. It's gotten so bad that there is some evidence that the Forest Service is trying to move the trail, but I'll have to see it to believe it.
The great thing about Plantation Trail from both a hiking and cycling perspective is that you are never more than a few miles from the Canaan Loop Road, so if you need to bail, you are just a short connector trail away from a main forest road. Plantation Trail is also fairly level (not much altitude change), so it is goo for distance hiking and cycling. I hiked 16 miles on Monday. The birds were so great that I could not stop.