As others have remarked, the exterior of the building is slightly austere - but this is how it was built, several centuries ago, and inside, is a very different story.
We stayed for three nights in Iona's Room - top floor, so especially good views over the tiny harbour and the coastline. A huge room, with two single beds linked together to make a superking-size. Quality furnishings, bedding, towels, etc..
Breakfasts are excellent, with a very wide range to choose from.
Evening meals are of a very high standard, and worthy of a posh/pricey restaurant in the cities. No matter how full up you are, try to leave room for the selection of homemade ice-creams!
Nothing seemed to be too much trouble, even our early start for, and late return from, St Kilda. Staff were so friendly and helpful, advising on best beaches, etc..
Neither accommodation nor food is particularly cheap - but nothing is, on the islands where so much has to be transported at exorbitant fuel costs, and here you do get what you pay for.
We are already planning to return next summer.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC