The trail surface is smooth and very runnable, with no major climbs/descents to speak of, though there's a fair amount of elevation change if you cover the whole trail.
Just be aware that traffic is high during peak times and on weekends.
This trail is often described as remarkably remote feeling, despite its proximity to Portland. It's one of the more popular trails in Forest Park, and is open to all types of trail users. As mapped, you'll start out at Germantown Road on the north end of the trail, and should you choose to go the entire distance, you'll turn around at NW Thurman Rd. However, that would be quite a long run, so the best advice is to just start at either end and go as far as you want, then turn around.
Enjoy the peace and quiet along the way - it's easy to zone out as you take in the sounds and sights of the forest, and forget how close you are to the city.
The trail surface is generally smooth and wide, so there's room for the many bikes you'll likely see along the way. It can and does get a bit muddy. There are white concrete mile markers the whole way, and it's nearly impossible to get lost.
Flora & Fauna
The trail is mostly in deep-feeling forest, with maple trees and alder, and of course, evergreens and ferns. And with that comes plenty of birds, whose chirping drowns out any noise you might otherwise hear from industrial zones across the river.