They accepted the proposed increase from HCAD, which was the maximum increase allowed. I did not find any support that they disputed/negotiated the amount and their customer support was awful when I tried finding someone to give me background. Customer support was essentially non existent.
When I couldn't find any realtors that would provide me comps anymore this past year tried them. I knew I couldn't argue condition so needed comps to argue unequal treatment. They negotiated the CAD to within 1% of what I was originally thinking was my target without me even having looked at comps. They took awhile but during the extended "not hearing results period" I would occasionally get an email that it was still in progress. All in all no complaints.
I've used them for 3 years. no complaints - they haven't done much for me though because i think the CAD was close to market unfortunately on my main house. but the service is easy to use. i did save on a second property that was super inflated and in rough shape. they saved me 800 bucks which i was happy for. it was an out of town property that i didn't have time to get to.