The first official driver fully working for RT2870 chipset for Yosemite 10.10 so far.
Download the beta driver from this site:
http://store.bearextender.com/pages/regarding-yosemite-compatiblity (Click on BearExtender 1200/Mini/Original customers)
Download the beta driver from this site:
http://store.bearextender.com/pages/regarding-yosemite-compatiblity (Click on BearExtender 1200/Mini/Original customers)