A few months ago Microsoft released a new RDC app for Mac named Microsoft Remote Desktop. This replaces Microsoft’s previous RDC app for Mac named Remote Desktop Connection.
Microsoft Remote Desktop is available via the Mac App Store for free, and has been updated twice since released. It supports OS X 10.6-10.9, and most users have reported it’s much faster than the older Remote Desktop Connection app. On my Mac it is substantially faster when RDCing into the Windows servers at All Covered Chicago.
Microsoft Remote Desktop has many bugs that have been reported with it, mostly involving multiple displays and running it in full screen mode. Unlike Remote Desktop Connection, it support running multiple RDC sessions at the same time. Microsoft Remote Desktop does not have the ability to import settings from Remote Desktop Connection, so all RDC connections will need to be added from scratch.
Both the new Microsoft Remote Desktop and older Remote Desktop Connection can be installed simultaneously on a Mac, so if you’re currently running the older Remote Desktop Connection there is no risk in installing and trying out Microsoft Remote Desktop. I personally prefer it, and I’m sure that Microsoft will be updating it in the future to resolve the outstanding bugs. https://itunes.apple.com/us/app/microsoft-remote-desktop/id715768417?mt=12&ls=1