Tom,
Can you elaborate on why a square cut is "very important"?
Now I can understand the concept that if a cut is not square, you in effect have less pipe in contact with the fitting and therefore a weaker joint. As an extream example, if a pipe should sit 1" deep into a fitting, and the diameter of the pipe is 1", and your cut is at a 30 degree angle from being square, that means one edge of the pipe goes in the fitting the full 1", but the other side only goes in 1/2". The end result would be only 2.25" sqare inches of surface area joining the pipe and fitting where there should be 3" square inches, and you have a section of the joint that is only 1/2" long rather than the designed 1".
But even with practice, I would say that my average cut on a 1" Sch 40 PVC is 1/10" to 1/16" out of square (i.e. the average fitting should cover 1" of pipe, and my typical cut had 1" of pipe on one side and 9/10 to 15/16" of an inch on the other. That means that what should have been a full 1" joint propably equates to the pipe only being inserted 95% of the way into the fitting. You don't think that that is good enough?