Brief report:
Although we took climbing hardware (6 screws, 4 cams, mixed set of nuts and hexes, carabiners, quickdraws, cordolettes and runners) and a 9.8mm x 60m rope, Tom Hartger and I ended up soloing the North Couloir in about 1hr 20min under "cruising" conditions - perfect neve (firn). We each had 2 tools. The 4th class ramp/low angle dihedral people talk about looked like 3rd class to me. We started at the base of the couloir at 8:20am and summited two hours later at 10:20am. There was not even a single cloud in the sky, sunny, a bit breezy....just a beautiful day in the Sierras. We descended via the class 2 SE slope towards Treasure Col and down the drainage back to Treasure Lakes trail and South Lake trailhead.
Additional info about climbing Mount Gilbert can be found here.