Whichever way you ride this trail, it will involve at least two killer climbs (at least one serious hike-a-bike if heading North to South). Even with the hike-a-bike, I prefer North to South. First, you get the very rapid altitude drop from Midgley Bridge down to Oak Creek. Beware--crossing Oak Creek during high water can be treacherous. Then there's some nice creekside riding. Then comes the BIG climb with 2 foot rock ledges--you will carry your bike up these. Once up on the bench, you get great views of Sedona and all the surrounding red rock formations. Then it's another rapid drop (very fun/moderately technical) to a large wash and then the final climb out to Schnebly hill road. You can combine this all the North Sedona trails by starting at Thunder Mountain and taking the city streets back to finish for a killer loop.
The north trailhead starts at Midgely Bridge on 89a about a mile and a half north of Uptown Sedona. The south trailhead is about a mile up Schnebly Hill Road west of 179.
http://www.singletracks.com/item.php?c=1&i=3064