I stayed here for a night and found the house and the service both above average. Be warned that the bed-and-breakfast experience in Duluth, while a good cultural activity, is extremely expensive. One night in the Olcott House set us back $194 (with tax, and the mid-week discount) and while the experience was quaint and unusual, I'm not sure it's worth the price. I would have rather taken a Holiday Inn downtown for $80, but maybe I'm too utilitarian.
The master suite we had was large and comfortable, though I thought the tv in the room was extremely small (a 13-inch LCD) and the bed was a little too springy. The decorations and furniture do a good job of replicating what this 1904 mansion might have felt like in its heyday.
The owners seem to have changed since the last reviewer stayed here, so we had to start from scratch in getting a vegan meal. Fortunately, a co-owner/chef was extremely accommodating and went out of his way to studiously check pancake ingredients in some pre-made mixes, before ultimately deciding to use some online recipes to make us some from scratch. For a first-attempt, I must say the pancakes were excellent: soft, fluffy and delicious.
If you're coming to Duluth for a special occasion, Olcott House or some other bed-and-breakfast might be worth the money, if just for the experience (most will run you $150-$250 a night, without tax). The majority of them are located in the North Shore area, fairly close to Lake Superior, though a bit too far from downtown for my likes. Otherwise, get a cheap hotel downtown or on the shore and do your own vegan-catering.