I have tried, so many times.
I get a white screen or error message every time I try to load MC with buildcraft supposedly installed. Yes, I've got mod loader, forge etc.
I've asked on pretty much all related forums, (MCforums, buildcraft forums etc) and they've all either said make sure you've got modloader/forge, or deleted META INF, which I have.
i've followed tutorials and instructions for mac to the word, and it still doesn't work.
I used to use technik as an automated way of installing it, with no hassle.
now however, with your new not-real minecraft launcher, I can't.