It's a decent network printer. Notable positive aspects: It can scan in colour (even though it's nominally a monochrome printer). It can scan while doing a big print job.
Configuring the linux support was easy. I told cups to use IPP to http://<printer>/ipp and use a PPD file I got from openprinting.org. Brother's own tool brscan3 configured sane to talk to the scanner.
Notable negative ones: There are several powerful blue LEDs. The printer makes a buzzing noise for a few minutes after finishing a job. Printing fullpage graphics is slow.
(Update: I've now configured the printer under Windows 7, Mac/Lion and Linux. Windows was the most difficult, Mac/Lion the easiest.)
The IPv6 support requires a reboot to work. Click the relevant buttons to enable it, then reboot the printer, then look up the IPv6 configuration in the web UI again. You'll see the IPv6 address near the bottom of the screen. It should look roughly like this: