Sitting on the fence about getting the remastered versions. Have previously bought them twice before with alleged new improved sound(?). Are they really that much better than the original releases? Is the extra material worth it? In my experience the extra material that didn't make it onto the album rarely rates as anything more than filler. IMO, the original vinyl sounds best with the best music available.. What is your opinion?
Well, it took me a long time to convince myself to buy them as well, since I've also bought these albums a couple of times before, but I gave in to a mix of brain washing from reading about the reissues everywhere, good old curiosity and a slight degree of fanboyism. I have not listened to all three albums all the way through yet, but I think the extras actually make them valuable additions. I don't know if you are interested in stuff like backing/instrumental tracks (for example of "Thank You"), demos, remixes etc, but I think they are interesting, especially the backing tracks. If stuff like that does not interest you, at least the bonus disc of “Led Zeppelin” with an unreleased concert from 1969 should. As for the sound, I think the sound is great, the volume is obviously higher, some things are more clear and the low-end rhythm section has definitely been improved - which is probably the most important aspect of the new sound, but whether they sound better is up to each individual to decide. Like you, I think the old albums already sounded great and never really needed remastering.
This is probably less important, but I also want to comment on the packaging, which is really cool. They've stayed true to the original layout and the booklets have some cool photos, but no liner notes (a slight disappointment imo). "Led Zeppelin III" has the spinning wheel, which is awesome and I believe, for the first time on a CD version(?).
In conclusion, I think you should definitely get “Led Zeppelin”. The rest depends on how interesting backing tracks, demos and remixes sound to you.
I hope that was at least a little bit helpful.