Going down is awesome. Riding up would be brutal(ly awesome)!
The best way to ride the Shafer Trail is to bring a support vehicle (one with 4WD and decently high clearance). If you're into a sufferfest, by all means climb your way out of there. You can also include it on a much, much longer ride like the White Rim Trail. But if you just want to experience the epic ride down, you can start at the Shafer Trail and wind down to Shafer Campground on Potash Road (which is also home to amazing rock climbing). Have your car follow and pick you up at the campsite. For the best biking guides in Moab, hit up Western Spirit and ask for Tim and Zoey.
If riding isn't compelling to you, it's also a great spot to catch sunrise.