Brother MFC-620CN testing conclusions
Ethernet connectivity works just as well, including for scanning, but the setup of IP numbers, and various other settings show up only when connected via USB.
The wireless connectivity called NC2200w is utterly useless, as there is NO network scanning for MacOSX.
The manual recommends connecting the Brother MFC-620CN only to a built in USB port, and a maximum cable length of two meters. I use an unpowered USB hub and more than 5 meters of USB cables via various USB extension cords and had no connection troubles at all. USB Printer sharing in MacOSX 10.4 Tiger works reliably, too. Scanning to a connected Flash memory did not work for me, but using the Brother MFC-620CN as a USB based Flash memory reader/writer is ok.
The document feeder is very practical and works reliably, but scanning speed is much slower than on a HP2710, that I tested a few days ago.
So all in all i still recommend the Brother MFC-620CN, as it is the only all in one device with built in answering machine and fax switch. But if Brother would take a look at the HP2710 and improve the sucessor of the Brother MFC-620CN accordingly, the next Brother AIO might be the perfect AIO machine.