I've stayed at the Grand Sheraton three times, and all visits have been fantastic. The main floor is especially noteworthy because it is built within the shell of a 100 year old marketplace with 50 foot ceiling and glass clerestory windows. The lobby bar is a perfect place to stop for a martini and offers good food in an attractive environment.
The rooms have recently been updated and are now at the luxurious end of what you'd expect from a Sheraton (almost Westin quality). They have really cool window seats that are perfect for checking out the skyline or people watching on the streets below.
The prime downtown location is convenient to the state capitol grounds. Unfortunately, that means a high volume of business travelers on expense account and the room rates reflect that.