The Rainbow trail is steep and narrow in places with many root and rock steps. It winds through gorgeous forest and is a blast to ride down. This wouldn't be my first choice as an uphill option as the first ~3/4 mile is very steep and difficult to climb. The last half mile has a long series of root and rock steps where the trail is very narrow and somewhat overgrown by vegetation. That makes for a difficult combination on the way up, but a thrill on the way down.
In my book this trail is a bombing descent full of drops and fun grades that leads you through some very pretty parts of Crosier Mountain.