My dad, his friend, and I all met up at this trail to run this morning. We parked under Mopac (them along the street, me in the parking lot that is reserved for Austin High during the week) around 6:30 am on a Sunday and while there were many cars already it wasn't full close to full. When we finished nearly two hours later, this had changed: It was packed in the area we had parked. Needless to say, this isn't a place to go for solitude, but I like it because it's fun to see everyone out enjoying the area differently (walking, running/jogging, biking, boating).
Our mileage varies from the one shown on here because with the addition of the Boardwalk we were able to run all the way to Pleasant Valley and cross on the dam. After crossing the dam is the area with a couple of murals (mentioned above), so it's worth it to do these extra miles, both for the fitness and the sights.
The trail is easy, mostly granite gravel with a few paved parts. It's really nice to run on. There are a lot of neat sights, such as good vantage points of the downtown skyline, sculptures, the Stevie statue, and and some cool graffiti murals.