I bought a mandoline recently which proudly touted its safety system. eg, the mechanism that slides up and down the mandoline makes a rather large square covering the area around the slicing veg. I was attempting to julienne quinces (hoping to evenutally make a dice), and pressed down very hard, my hand slipped and I julienned the side of my wrist. I had to go to the emergency room--luckily they had some special glue so I didn't have to overcome my needle phobia then and there. Lucky too, that it didn't hit a vein.
The point is, even though it SAYS it was built for safety, be EXTRA EXTRA careful with very hard items such as quince. I had only used it once before, with carrot, and that did not struggle to slice. So I guess the rule is if it starts to struggle, switch to a good old fashioned knife.
That said, if you ever need to slice meat, I've discovered it will have no trouble whatsoever.