I was invited to do this trip with friends, taking advantage of the last weekend before the number of climbers allowed on the mountain is restricted to 100 per day.  Permits are always required to climb above 4800' and cost $22/person (free in the winter, Nov. to March).  You should check the forest service website for more information on registering, costs and picking up your permit.
We chose to do the standard winter route from the Marble Mtn SnoPark via Worm Flows.  As mentioned, this was the last unrestricted weekend for climbers and according to the folks issuing permits, there were 250 climbers on the route this day alone.  It did look like a line of ants on a pile of sugar at times.  There wasn't a problem following the route or having to kick steps.
My first trip a big mountain and a very impressive one at that.  Views between cloud layers as we ascended were awewsome and into the crater from the crumbling rim incredible.
We got a little glissade greedy on the way down and got off route, following Monitor Ridge to far down.  We needed to do a 1/2 mile traverse to get back to the trail.  Great trip and a lot of fun.