It can be hard on your heart: dangerous if you use it while exercising/hot or if you have an underlying heart condition. Still it's not nearly as dangerous as other stimulants.
If you are doing a ton of ephedra daily, I'd recommend you get off it -- the biggest risk seems to be that the tolerance removes most of the positive effects, and so you need it just to be normal -- plus having chronically high BP from it is not a good thing in general for your health.