I think that part of the fear factor of OmniFocus is that we don't know how to take advantage of the various things available in OmniFocus.
I'd suggest getting a copy of "Creating Flow with OmniFocus." at
http://usingomnifocus.com/
If you click on the resources link at the top of the page, you'll find a list of articles about utilizing OF. But the true gem is the eBook. It shows you different workflows and will ease you into some of the more powerful stuff like Review, flagging, etc.
Once you learn how to tame the beast called OmniFocus, you can become a true master.
I see the various posts about multi-colored flags, tags, etc. At first I thought it was a great idea. But then it becomes a bit more complex and may become unwieldy if not used correctly. Suddenly, you'll have multiple colored flags and you can't remember what they mean because you have so many colors. You'll have so many tags that you don't know why you made them in the first place.
If done right, tags and flags would be beneficial. If overdone, they can just complicate your GTD system even further.