Biotin (also in prenatal vitamins and recommended if you want to grow your hair faster) was great, great, great for my hair and nails. I grew out my hair for my wedding waaaay faster than I ever have before. But I'm also prone to acne and it made me break out like a woman with chicken pox, except all really big pimples.
My nails are generally one plain color, though I sometimes blend paints to come up with new colors, or layer them. I can't do much painting with my non-dominant hand, so if I were to do any details, they'd have to be on the right.