The majority of bases are non slip, but i've heard a few stories about some not being, so be careful when getting yours, and either buy one from a store or check one out if you can before buying it online if it works out cheaper.
Don't forget to check the non slip qualities of these paints as well ( freddymercurystwin made a good suggestion ). I've seen some garage floors done with the paint and as soon as any water is on them they turn into ice rinks, which will probably make stairs twice as lethal. Use a non slip...