I use the SCC embed capabilities of FCP7 all the time to output captions to SD and HD formats. You just create the SCC file with MovieCaptioner, attach it in the ETT function, and rock and roll. It is so easy once you figure out the deck settings, etc.
Now it looks like I’ll be editing in FCP X, then dragging my finish movie file back into FCP7 to output to tape with captions. Some of the other programs mentioned above may work, but I’ll be sticking with what I know, and will NOT be deleting FCP7.
Extra work is never welcomed, but hopefully the upgrades to FCP X will be worth it.