The Duke of Richmond is an excellent base for a visit to Guernsey. The rooms are a good size and are clean, the staff are particularly friendly and the food is well above average. The location is good, too: about a fifteen minute walk up hill from the main street, though quicker if you're fitter.
The downsides? None really. The relationship between the stairs and the lift is somewhat quirky - you go up in the lift, then down some steps to your room.