I am a Weekday Select Passholder and I go to WDW two to three times a month. Last year TP was quite reliable. This year Disney has been doing a lot of things to shake things up, and TP has only been accurate enough to tell me which day of the week is less or more crowded and which park is less or more crowded. I have yet to find a day when the parks haven't been two or more levels above the prediction.
However, I will say they have definitely been more accurate than any of the other prediction bloggers out there.
Use them for a guideline this year. Make a plan. Get your Fast Passes and stick to your plan. Be willing to go on less popular rides. Plan a break in the middle of the day when it's most hot and crowded.
Next year, I think they will have their groove back.