A great Hike. Like others say, start early.....we started at 8am but 7am would have been even better as if you plan to do Primative loop as we did then the last 45 minutes back to the Landscape Arch (assuming a clockwise loop) could be a little punishing if not adequately prepared on a hot day.
The Arches are all fantastic in their own way and quite unique. We enjoyed a treat of mother and young deer feeding at Landscape Arch which was great. If you choose to take the Primative loop and assuming it is dry then there is nothing too difficult although if in doubt spot the cairns (rock piles) which indicate the way. Also around Double O arch of you wish to find the Primative loop (again clockwise) then pass through the arch and pass around the fin to find the trail. That was the most difficult part of the trail to stay on. We took just over 4 hours with 2 children (15and12. Very rewarding hike. Primative Loop only has one arch (Private Arch) which is beautiful but for the less confident then just turn back after Double O arch would be my suggestion.