When I parked the car in Ossining near the beginning of the trail, somebody asked me whether I had brought my machete. Taking this as a joke, I set out undeterred.
The very beginning of he trail is poorly marked. It starts to left of a long driveway which parallels 9A. At some point, one has to just see the trail and cross over some weeds - no sign for the trail. After a few hundred yards, the weeds are starting to take over and the trail narrows to less than a foot. Later, there is a large tree that fell across the trail and the only way to get past it is to crawl underneath as there are thorny bushes to the left and right. There are a few more similar obstacles.
The trail improves somewhat once past Grace Lane and at times is very pleasant, although near road crossing the neighbors seem to have used the trail to dump garden refuse or trash, in particular at Rte 134 and Croton Dam Road. At times, the trail is poorly blazed and it takes some attention to stay on track.
The trail is outright enjoyable once it enters the Teatown park area, with a side trail to the waterfalls, a few clearings under powerlines, and well maintained wooden walkways across muddy stretches.
Further North past the Croton Dam, for about 1.5 miles the trail is on Rte. 129, Mt. Airey Road and Colabaugh Pond Road. Not very enjoyable, but oh well. Starting right at the corner of Mt. Airey Road and Colabaugh Pond Road, there is a short stretch through the woods before again going onto Colabaugh Pond Rd. It then again enters into the woods for a nice stretch along the the Northern half of Colabough Pond. The trail crosses Colabaugh Pond Road, but I never found the trail on the Northern side of the road and ended up going through the woods (probably over private property) using the GPS. Once crossing a stream, I finally hit the trail again after about 1/4 mile. I hindsight I believe the the trail entrance is probably further down the road than indicated on the 2 maps I carried.
From here, the hike is nice and the trail well maintained all the way up to Blue Mountain. I enjoyed the variability in terrain from flat to undulating. Blazing was fairly consistent even though orientation was easy - just follow the noise of gunshots from the shooting range about 2 miles North.
Overall the trail had several wet sections, from just muddy all the way to ankle deep water. I recommend wearing waterproof boots - or flip-flops as my daughter would. (I hiked the trail after a week of heavy rainfalls, so some of this muddiness may be better later in the summer.) The terrain is relatively flat with a few easy inclines as you get further North. Also, the trail get rockier towards the North - another reason for sturdy shoes.
While I don't mind less than perfect trail conditions, the Southern end really could use some maintenance. Many of the blazes were old, and on some stretches, where the trail paralleled other trails (Teatown, around Colabaugh Pond and in Blue Mountain) the prevailing blazes were the local ones and the green blazes only occurred occasionally. Because of that I recommend to take a map (e.g. the one on the Westchester County website) and read the description in Walt Daniel's "Walkable Westchester". Maybe because of these issues, I only met one other hike and one biker along the entire trail. That alone more than made up for all these small annoyances.
Overall, I enjoyed the hike as it is one of the longest continuous trails around. Because of that distance and its other challenges it is a nice training route for longer hikes, but it is not your regular "walk in the park".