This will be my first post on the new WTF forum. I’ve never owned a grand piano. After reading your post Shiro Kuro, the following came to mind:
If it was a local move, did the piano mover come out to your house BEFORE the actual move to scope out beforehand what’s involved between unloading the piano out of the truck and moving it into your house?
Regarding the movers not using a ramp. Maybe they had a ramp but couldn’t use it. Ask them why. Does your house have a porch with curving stairs or is the staircase longer than the length of a mover’s ramp?
Concerning the thud sound when the piano was on the sled: It appears that piano moving sleds need to have springs mounted on each wheel to act as shock absorbers. Yeah, I know they don’t make them like that but maybe they should.