I've been up there a few times on dual-sport motorcycles. It's a pretty good road, certainly doable on a CX bike, although a MTB would probably be more fun coming down. It is a pretty tough/long climb so you'll need low gears unless you're an iron man. I remember one slightly dicey spot where the road narrows with steep dropoffs, but it's not technical at all and there is plenty of room for a big SUV, so you won't have any problem on a bicycle unless you do something super stupid. I don't recall whether there was water available along the way, but it's only about 15 miles up from the general store at Mazama, so I would think you could easily just pack in enough water for the round trip.
It's a fun trip. The views at the top of Slate from the lookout are stupendous. It will probably be cold and windy even when it is pleasant and hot in the valley, so have some extra layers, a hat, and gloves. I'm not sure I'd put it in the class of "You haven't lived until...." though.
If you drive over, I'd camp at Pearrygin State Park just N of Winthrop which is a much nicer campground than Early Winter.
Last edited by markjenn; 02-10-13 at 04:27 AM.