I take Concerta, which is the time release version of ritalin. I have had no problems with it at all. I take 54mg per day. It helps quite a lot. It gets my brain activity as normal as it can get. Just lift heavy and eat big, it won't hold you back.
Just a note for people without ADD. I have no sides, because it just gets my brain activity where it should be. People without ADD could have some problems because some parts of your brain could become overactive. But that is with any stimulant.