The Admiral, with some encouragement, climbed his cat stairs today. The key was that I actually pushed his hindquarters off the ground. Suddenly he realized that the stairs weren't simply a layered treat buffet. He climbed the remaining three steps and then continued into the bed, where he was lavishly rewarded.
Here's a bad camera-phone picture of the Admiral and his stairs:
The chair to the left of the stairs was his previous mechanism for bed access.