Yes, 90 to 95% of appeals are successful for property owners who appeal at informal, ARB and judicial appeal.
There are two levels of appeal. 
Administrative appeal – Informal hearing and appraisal review board. Depending on county, about 60 to 70% get a reduction.
Judicial appeal – legal appeal. Over 90% generate a lower taxable value. Owners who use both the administrative and judicial appeals have a 95%+ chance reducing their property taxes.
For 99% of owners, the appeal ends with the administrative hearing. O’Connor commercial clients receive the benefit of O’Connor coordinating a judicial appeal at no cost unless we reduce your property taxes. Really. O’Connor pays the attorneys, expert witnesses (2 expert reports for most cases), and filing fees. It’s a no-lose proposition. (O’Connor routinely coordinates judicial appeals for commercial property valued over $750,000 and houses valued over $1,500,000.)
No other property tax consult pays all the costs associated with both levels of appeal. O’Connor commercial clients with values over $750,000 can expect a reduction in assessed value most every year, based on using both levels of appeal. 
There are no flat fees or upfront costs with O’Connor, and never a fee unless we reduce your property taxes. Simple and fast enrollment is free at: or call 713-290-9700. Fast and free. 
P.S. Just 2,250 appraisers generate initial 2021 assessed values for over 20 million tax parcels in Texas. Can they possibly be accurate?