It gets the job done

This is pretty middle of the road. It does a good job of picking out some of the low-hanging fruit, but it's not going properly evaluate semantic structure and will pop several false positives. Additionally, the tools are incomplete. For instance, the contrast editor will allow you to test your colors with sliders so you can get the closest color that passes; however, that isn't how color palettes work, you generally don't get to change a companies palette without a lot of pain; furthermore, there is no ability to adjust the font-size and both font-size AND color are used to determine contrast requirements. Oh, and they use points VS pixels...nobody is using points on the web even if the ADA uses them in their fairly dated guidelines. Text from the actual contrast editor "Text is present that has a contrast ratio less than 4.5:1, or large text (larger than 18 point or 14 point bold) has a contrast ratio less than 3:1.". 14pt = 18.66 pixels, so I can see their logic even if I don't agree with it.