It really depends on where you are leaving from. The majour airports you are usually ok as long as it looks about the right size and weight. The smaller airports tend to be more of an issue.
For myself I have found Red Deer (YQF) to be the hardest to deal with. Every time I have gone out of there they have weighed and sized every bag. I was over by 1/4 a pound so they made me check it. Laptop screen got smashed. Still not happy about it.