I've been to the top of Miller several times. I actually stayed overnight once when the fire lookout cabin was still there. That was pretty cool. This was my wife's first time up. We did it from the top of the Carr Canyon road which helps cut off some elevation, but lengthens the hike. That's actually where I have done it from before each time too. The first stretch of trail out of the car park area is really rocky. So when you return from the hike, this section is something you wish wasn't there. There are many sections of burned forest along this trail. It's a shame as it was a beautiful forest many years ago. The views are much better of course, but sad that the forest burned. When you get to the cut off to Carr Peak, the trail becomes fairly easy as it skirts around the south face of Carr Peak and descends slowly to another trail junction. Here the trail joins the Arizona National Scenic Trail for the rest of the way to Miller Peak. There is also a trail that goes down Miller Canyon. From here the trail is pretty easy as well as it follows a crest. Once at the base of Miller Peak, it is a pretty good climb to get to the top. With the fire lookout no longer there, it looks a lot different on top. Excellent views all around though. We did this in late May of 2015 and the lady bugs were all over the peak like they usually are. It is a long day for sure, so one needs to leave fairly early. Feet will be sore by the time you get back :)
This trail is my new favorite. I don't recommend this trail to young children or old dogs. I had to carry my 10 yo, 80# dog the last mile to the trailhead. Not fun.
Whilst hiking this beautiful trail be aware of rock cairns and switchbacks. For the most part the trail is pretty clear but there are a lot of game trails which if you aren't careful can get you scratching your head.
There is plenty of canopy on this trail and about 6 or 7 degrees cooler than regular. You won't be disappointed on this trail. Waiting for the monsoons so water will be readily available.