To do a complete de-volving of the SE's it takes more than lifting out a few shots and scenes.
The biggest thing is to restore the colours of the OOT using the 04 dvds. As explained here with some screenshot comparisons.
http://originaltrilogy.com/forum/topic.cfm/Auto-correction-from-SE-colours-to-GOUT-colours/topic/6732/
The biggest example of this is removing the blue tint from ESB. This also serves to match the 04 dvd footage with the GOUT footage.
Little things like the realignment of horizons in SW I could live with out but the people undertaking these projects are pretty thorough. If you're going to do it you might as well do it properly. There's even a few SE things from SW I'd leave in but I don't have the tools or know how.
The things some people have done like removing the cg Rontos (sp?) from Mos Eisley is incredible. Even things like restoring the lighsaber blade colours.
Paulisdead's Vintage edits are the projects I'm watching closest.
They can be read about here:
SW Vintage Edit: http://originaltrilogy.com/forum/topic.cfm/Star-Wars-The-Vintage-Edit/topic/8069/page/1/
ESB Vintage Edit: http://originaltrilogy.com/forum/topic.cfm/The-Empire-Strikes-Back-The-Vintage-Edit/topic/7634/
I recommend checking them out, even to just look at the screenshots. It's amazing.
To quickly summarise, ESB was the first project he tackled. It's not perfect and in the future he wants to do a v2.0. SW is the one he's working on at the moment but is not yet finished. I guess ROTJ will follow next.
edit: And as far as I know Paulisdead is using HD broadcasts as his source.
If I've made any mistakes please correct me as I'm mearly a lay-man.