I have ordered from CMP several times, both Garands and Springfields. Generally happy with the (20 or so) rifles I have received. The key to satisfaction is to understand exactly what you are purchasing. Almost all of these old relics have been in service for decades, many have been loaned out to friendly nations for years, and most have been arsenal refurbished one or more times. "Service grade" generally denotes rifles that meet the minimum requirements for issue (muzzle erosion, throat erosion, etc). "Rack grade" is a lesser overall quality.
The all correct, original condition rifles go into a special category for auction. These may be pristine, but more likely are also well used. Collector interest is the primary consideration, so a relatively uncommon receiver and or barrel combination could become a high dollar auction rifle.
You want a good shooter? "Service grade" will usually provide that.
You want a representative piece for display? "Rack grade" will probably fill the bill.
You want an all original, pristine piece of American history? Look into the auction items and get ready to open up your checkbook.
Best regards.