I appreciate everyone's input on the topic. Just to reiterate the point - -I am very happy with the interactions that I've had with my general contractor.
The more time I spend out there cleaning the slab off (after every snow!). I really don't think it will cause me any problems. Once the building is complete I will move a few tool boxes etc. in to make sure, but I will likely just spend the money on more tools versus redoing the floor. I may grind the form marks off of the foundation walls on the inside though - - just to get rid of the visual reminder of the slope - they are level and close to the floor and make it very visually obvious that there is a slope..
So far, they've gotten every other detail that I wanted right on. They poured the slab thicker in the bay for my lift and it has plenty of steel in the floor. I know they say 4" of reinforced concrete is adequate, but.......... I just wanted it to be overkill I suppose.
I'm getting really anxious to get the shop done so that I can start tinkering. I'm hoping to have it pretty well wrapped up by Summer (remember, I'm finishing the inside out and wiring it etc. and I'm slow!) and get started on my next major project.
I agree with some of the earlier posts - - If it is important, make sure it is communicated properly and documented.