I'm using Remote Desktop for Mac on my base Retina MBP.
Remote Desktop is incredibly slow for connecting to my Windows 7 PC.
Why is to so slow? Are there other alternatives that will work faster?
It's impossible to know why it may be slow without having access to more detailed info about your current setup. However if you want to try alternatives to check whether it's consistently slow (and therefore perhaps infrastructure based) or just the MS app that's slow, then you can do worse than try to use CORD which is a nice open source remote desktop alternative that's free.
You can also try Ericom Blaze, which is an RDP acceleration and compression solution. Blaze can accelerate the RDP connection by up to 10 times normal RDP.
Get more info here
Please note that I work for Ericom.