Once a new cartridge failed ("not recognized" error even though it was purchased through Staples) and the brother support person walked me through some secret squirrel reset code which I of course saved for future use. The fact I could get someone from the company on the line to help me was a rare experience for tech companies.
My only gripe with the toner cartridges is the requirement to enter a serial number to get a recycling mailing label. The serial numbers are miniscule.