Despite never printing in color, it slowly burns up the color cartridges.

Either the cartridges are not reliable or the printer is defective.

Tech support decided my black cartridge was also defective

I'm going to try the LD compatible cartridges.

Tech support determined that the cartridge was defective and overnighted a new one

I got tired of the expensive ink cartridges for the ink jet printer.

and disallowing non-Brother cartridges.

The bottom line is that if you print a lot of small jobs, there will be a substantial reduction in the amount of the toner you can actually use before the cartridge is expired

Out of the box, we have the error code telling us that a non-genuine toner cartridge was installed

If they're not as good as the Canon cartridges I'm going to chuck them out.

In the end I decided that (a) Only about 16% of the reviews were negative, (b) there was not a single compelling complaint theme running through the negative reviews, (c) it was worth risking $350 in the hopes of avoiding a $1000 and up expenditure for a more commercial printer.

The printer apparently layered all the colors (and black) to make the "black" text (it also slowed way down as it was processing).