Today's printed fabric can be as far as an inch off! If you want a real challenge, try working in a fabric store and explaining why your straight cut doesn't look straight many times a week! Whenever I am using one of those, I use it in a pattern where it doesn't matter at all. It won't work to try to force it to look straight.

Drives me nuts when that happens. I make it even more off to make the crookedness look intentional.

And having to explain why you cut their plaids and checks with scissors instead of the rotate cutter.