I have redirected all my Documents, Downloads, Music, Pictures, and Videos to my SD card. I've been doing so for several years and it has worked great. I periodically backup all the items on the card to an external USB drive.
I agree with the previous posters. An SD card has saved my life, especially with my Surface 2. I have the 32 gig version of the Surface 2 and that space was eaten up in about 2 months.