We camped 2 nights at Terror Basin before and after the climb.
See my trip report at WTA for current conditions.
This is a very difficult hike, for me at least. More exposure than I'm comfortable with. Some very steep snow slopes (going down to Terror Basin from the "notch", as well as going up to the col before McMillan), and fairly steep rock/scree scramble from the col to the top. A couple of snow bridges are about to collapse on the way. I'm not sure if earlier or later in the season is easier.
We parked 1 mile from TH. So the total is maybe 12 miles one way, more than 9-10K' gain. The camping area is 6000' gain, maybe 8-9 miles.
Incredible view. Hard earned.
Gears we used: ice axe, helmet, crampons. All absolutely necessary now.
Note, you need a permit to camp here. Day-of and day-before permit can be obtained at Marblemount's Wilderness Info Center. It's open 7-4. A long queue on Saturday morning.
Attached photos:
1) camp site. I drew the outline of our climbing route. In later season, you go down to the green lake and up, more straight, but more elevation gain.
2) view on the scramble to McMillan
3) one of the steep sections in the forest.
4) camp site. I drew the route coming and leaving the basin from the "notch".
5) an example of a narrow snow bridge.