Most people say that these are not addictive and it's the main reason why they aren't banned. I was thinking about trying armodafinil as it's the improved version of modafinil and easily accessible where I live, but I talked to someone who tried using it and godt discouraged. It appears that the effects don't work wonders for some people. You can be a little more resistant to it. For instance that friend of mine took a normal dose and didn't feel anything, so the next day he doubled it and felt a slight increase of energy, during the day, but also couldn't sleep at night, so it basically threw him out of balance.
I also read about the side effects after prolonged use. Some people get like a hangover the next day or insomnia. I might try it anyway to see how my body reacts, but that's it.