Over the years the airport has incredibly gotten better, namely my adding more food and shopping selection and trying to make the security process better. That is for terminal 1 that I use very frequently.
Signage is constant and well detailed. It's a fairly large airport and thankfully there's plenty of moving sidewalks. Only downfall is that they can be out of service on a regular basis.
Security process can be a hit or miss depending on the day. The security officers can be either very lenient or extremely fussy.
The US customs hall has recently been rearranged and it makes the whole process more seamless.
Where there are still a lot of work to do would be the Canadian customs hall. It's always very busy, directions are lacking and the airport support employees barking instructions are just adding to the confusion.
There's a good offer for parking and a train shuttle allows you to go between the terminals and the economy parking.
There's also a express train that brings you downtown and 4 different municipal transportation lines.
Not anywhere near the European and Asian airports but thankfully not as bad as the American airports either.