I appreciate everyone's advice, thank you. I looked under the deck and it looks fine, just a little dirty-no big deal. The blades do feel a little dull and have small nics and dings in them but again, nothing huge. I just feel like they weren't honest with me. Years ago I worked in a large bike shop and we sold mowers as well, if I had sold a demo to a customer without telling them when they came back to complain the owners would've laid in me but good. You just don't do that.
I'm still unsure of what to do but I do know that I'm a little OCD and this will bug me if I don't say something. I guess I'll go talk to them this morning, I don't plan on being rude I'll be nice. I figure they can look at it as you had an interested customer and you let him try your demo out, he liked it and would like to purchase a new one. No harm no foul.
Thanks again everyone!