I have a cheap company-issued Dell laptop. My Mac is a Core i7 with 16gb of RAM and yet Excel (and all Office apps) run so, so much better on the Dell. I get that Microsoft makes Windows so of course that's going to be their priority, but the Mac apps are just poorly coded. There's no reason for them to be as sluggish as they are. I will be switching to a Mac for work soon, and I'm really disappointed that my Excel performance is going to drop so significantly.