The Cilley-Barber route is about 2500 feet of mostly snow with a few ice sections here and there. The crux of the route is more than 1000 feet up in a narrow, steep, and wildly wind-sculpted vertical waterfall. Even though it's only 75 feet high or so, the exposure makes it very exciting.
The route is about 16 miles from the nearest road, which makes getting to it a mini-expedition. You have to have a group of at least 4 people, and you have to apply for a permit to go into Katahdin. All of that is covered in the main Katahdin page, but we used skis and pulled sleds in to the Roaring Brook cabin on day 1, and then on day 2 we went up the much shorter but steeper trail to the Chimney Pond cabin. It was steep and narrow enough that we took our skis off for the last half of the trail.
At Chimney Pond there is a nice, toasty cabin with a wood-burning stove, and there are also some lean-tos (3 sided and not so toasty). We were lucky to have the cabin almost to ourselves.
To get to the Cilley-Barber route, you basically head out of the cabin and straight up toward the huge cirque of Katahdin that is right in front of you. It's hard to miss. You'll gain several hundred feet of elevation before you come to the lower ice section, where the actual climbing begins.
Be sure to check in with the ranger at his cabin (which is about 100 yards from the main cabin) the day before you climb so he'll know your plans. He can also give you the latest weather report and maybe some tips for the route and the descent.
The bottom ice section. Low-angled ice about 1 third of the way up. Approaching the crux.
The route itself is very easy to follow. It basically goes straight up from the bottom ice to the obvious crux (where the couloir pinches down to a narrow spot), then up, trending right to the summit ridge.
The lower section is about 200 feet of 3 to 3+ ice,
followed by a long (300 feet or so) snow ramp,
another, short, easier ice section,
another, short snow ramp,
another, longer, low-angled ice section,
then another snow ramp,
another, very short ice section,
a little snow,
then the crux.
By now you are about 5 or 6 pitches up, and the crux is a steep, grade 4 to 4+ water ice formation that is about 75 feet high. It looks ominous from down low, and you never know what crazy shape the wind will have turned it into. The exposure is fantastic.
After the crux, there is more low-angled ice and more easy snow to the summit ridge - probably 4 or 5 more pitches. We angled right because the descent goes right, but the line of least resistance should be fairly obvious.
To descend, traverse the ridge to the right, past the giant cairn (pile of rocks) that marks the summit and the northern end of the Appalachian Trail, and then head down Cathedral Ridge. If you hug the right side of the ridge, never venturing too far right onto steep terrain but trending right the whole way, you'll end up heading right for the ranger's hut.
We did this route in about 11 hours cabin to cabin
A nice, light alpine rack will suffice for this one, depending on how much gear you want to put in. We brought about 7 medium screws, 2 pickets, and a few pitons and nuts. We simulclimbed the whole route, except for the bottom ice crux and the upper crux. I don't remember seeing any fixed gear at all, so once you are committed to the route, it would be difficult and time (and gear) consuming to bail. It is never very steep, except for the 2 cruxes, so most of it could be downclimbed if necessary, but it's long.
Be sure to pay close attention to the weather, because it can be brutally cold up there. It is longer, colder, more remote, and much more difficult than anything on Mount Washington, so bring warm clothes, extra headlamp batteries, and move fast.