Its a mild trail. Honestly, the trails you rain while in red rock canyon are tougher than Miller. As Gunner stated the top can be difficult if you don't place your tires right.
While you are there, pop over to Gorman's Jeep Park. They put in some really nice obstacles. Would advise staying out of the deep water pit. Last time we were there we saw two paper tagged jeeps stalled in it. More for monster trucks than for jeeps.