Couple thoughts here. First, I might be missing something concerning the handling of RAW files in iPhoto 5 (but I don't think so). So the short answer is yes, you have to re-import the altered RAW file back into iPhoto 5.
My advice is, if you have a RAW workflow that you like, stick with it. It's nice to have RAW capability in iPhoto 5, but I wouldn't create a new, and possibly inferior workflow, because of it.
I can't speak for the iPhoto engineers, but I think I have an idea where they were coming from by generating a JPEG immediately from RAW data you import. It saves a lot of messing around and keeps things simple, which is still a primary goal of iPhoto, even as it matures.
I also know those guys pay attention to your comments, and we might see some new options in future releases.