We use Focalin as a booster and have for several years -- it's the same methylphenidate. difficult child 2 doesn't do so well on it any more, though. Makes him jittery and irritable (so does Daytrana patch -- same drug, different delivery system), but he IS able to focus and he is not as hyperactive. Concerta stopped working for difficult child 2 -- needed higher and higher doses to achieve same effect.
difficult child 2 does GREAT Concerta, Focalin and Daytrana (all methylphenidate), but his ADHD is pretty straightforward, with no mood issues.
My understanding is that there's methylphenidate-d and -l, and one builds up in the body and hangs around longer...sorry, my head's a bit fuzzy about it... I'll post more if I can find the info...