Yeah, ya know, I look at it like this: these aren't the movies I knew for the first 20 years of my life. Lucas' alterations severely impact my enjoyment of the films. On top of that, I have Harmy's "de-specialized" editions of the OT in 720P.
As far as the prequels go, I'll only watch the Phantom Editor's cuts of Episodes I and II (and then only rarely), and I haven't found a cut of III I'm entirely happy with yet. Generally, I don't pay much attention to the prequels.
If you're buying them just for the supplements, there will be far easier ways to watch the handful of cut scenes from the OT without buying the set, and you really only need to see them once.
From my point of view, I don't understand why people are buying them.