Prior to retirement I worked as an engineer at a local station and we found we had to get a consumer TV from Best Buy to actually see how our signal was performing. The receiver for our off the air monitor showed everything to be right even when the PSIP information or aspect ratio were not right. As Jeepguy said, using a consumer TV to monitor your signal you actually see what the viewers are seeing.
We have several stations here in the San Francisco/Sacramento area that are still transmitting the wrong aspect ratio. I hate it when they stretch a 4:3 picture to 16:9... and some are still doing that.
I recently worked with the owner/CE of a new local low power station that's offering 9 sub-channels on channel 3. The aspect ratios were wrong on a number of the channels. Some were stretched, some that should be 16:9 were 4:3 so everyone was real skinny, some were OK. He said they all looked good on his monitor, but he let me tell him what the aspect ratio should be and he adjusted each channel accordingly. They all have the correct aspect ratio now! They still look good to him, too.