Not specifically mentioning Mac drivers is probably not a concern since OS X supports nearly all printers, but I prefer manufacturers that visibly support OS X. I like Brother printers and multifunction devices these days. Their support is top notch.
Read this press release for a description of Brother models that support AirPrint - which is a nice (though not necessary) feature I'd recommend:
Canon and Epson are OK too, HP is a distant last.
It IS a concern, canon hasn't updated drivers for my selphy printer so I can't use it. My Epson multifunction had delayed driver release every time a new mac OS is released. I'm tired of companies that won't support mac.
I'm in the market right now for a new multifunction color laser and I'm buying whoever supports mac best. end of story.