Overview
Overall an easy hike. The entire hike is just walking up an old forest road. The lookout is what makes this worth your while. It's a newer lookout (built in 1996) and is still in use by the Forest Service. I can imagine the views are incredible being so high up, but when I was there it was raining and you couldn't see much ahead of you the entire time. The cab is locked, so don't be expecting you'll be able to venture inside.
From the stairs Getting There
From Estacada you will take 224 E for most of the way. Once you reach Ripplebrook you'll continue onto NF 46. Then in about 6.5 miles you'll turn left onto NF-4680. There is not a sign to indicate that you are in the correct spot, however you should see a gate indicating that the road is closed and that the road is not maintained for motor vehicle use. Park without blocking the gate and just follow that road.
Route
Just follow the forest road all the way up, it will fork once, but just keep going straight. 2.8 miles one way.
This is what the trail consists of the entire way up. Red Tape
When to Climb
All year, probably can't get to the "trailhead" when there's snow though.
Camping
Endless amount of camping options. You'll pass by numerous campgrounds on your way there.
External Links
http://www.forestlookout.com/sisi/sisi.html
http://www.nhlr.org/lookouts/Lookout.aspx?id=394