I have been quite happy with both B/W and Color laser Multi-Function Machines from Brother. They use standard CUPS drivers and provide TWAIN support for the scanning function. My latest is an MFC-9320CW (Color/Wireless) and it has worked flawlessly with my Macs as well as my iPhone and iPad. (Note it takes a free iPhone/iPad app to Print or Scan.)
I have also been quite pleased with a Canon IP4500 printer that I network wirelessly through an Airport Express. It too has been very reliable and like Brother, Canon keeps the drivers up to date. I have gotten the Canon to work with the iDevices using a third party app but it requires the help of one of the Macs to do its thing whereas the Brother App only requires both the printer and iDevice to be connected to the same Wi-Fi network.
