I'd like to say that I too experience a somewhat 'speedy' effect after each daily dose of Subutex. It tends to make me very chatty and almost excitedly happy. This still occurs despite the fact that I've been on it daily for nearly 2 years.
Also, it has an effect on my sex life. Following a dose of Subutex, I (and my partners) find that I can copulate at great length, with the stamina of a porn star. On those occassions where I've missed a dose, the effect has vanished.
After nearly 2 years, I still experience sleeplessness and constipation, the drug's only downside (in my book...), otherwise I'd have to say that it's saved my life, without a doubt.