I can only speak for the Pennsylvania and New York sections.
The good:
>passes through/by many of the region's highlights including Cook Forest, Allegheny National Forest, Letchworth State Park, Watkins Glen, and Adirondack Park
>features interesting natural features: old growth forests, conglomerate rock cities, deep gorges, scenic hills, and some of the region's finest lakes and waterfalls
>fairly uncrowded (even in Watkins Glen and Robert H. Treman State Park where the NCT/FLT bypasses the highly-trafficked gorge trails)
>interesting side trails such as the Tracy Ridge Trail in ANF and Letchworth's 25-mile branch trail
>plenty of campsites including lean-to shelters that see little use compared to other places like the Appalachian Trail and ADK high peaks
>although it probably won't be necessary, dispersed camping is legal in national and state forests if you camp away from trails, roads and waterways (half a football field away in NY's state forests and varying distances in Allegheny NF and Finger Lakes NF)
>avoids large population centers unlike the Bruce Trail in Canada
The bad:
>way fewer breathtaking vistas than the AT, CDT and PCT offer
>elevation changes aren't as dramatic, so doing the NCT isn't as bragworthy as thru-hiking or section-hiking a Triple Crown trail
>lots of roadwalking and trail reroutes resulting from landowners closing their easement sections
>unmaintained sections with blowdown, high grass, overgrown vegetation, and infrequent blazes (overall it's better now than it was 20 years ago)
>mosquitoes, ticks, spiderwebs, thorns and mud are not uncommon
