I too didn't have any issues with the ticketing system when I had a fault end of May (speed dropped below min handback). Kept informed by phone and email, even emailed a copy of the test results, both current and end of fix.
Complaints? None from me. The process was fairly quick and did the job.
Only thing I would say is that some people don't always help themselves. Even today on Plusnet's forum there is someone having problems and he/she quite openly admits to carrying out only a part of the asked for tests; go figure. Why bother asking for help!