I think it's a good film. I've seen it quite a few times and certain bits of it many times. Along with the updated version, it's a very long film and it can be hard to keep my attention when groups/artists I don't care for like Sha-Na-Na are on.
I actually went out and bought the original LP back in the 90s because I thought the Woodstock performances of groups like the Who, Country Joe and the Fish and Jimi Hendrix were superior to their studio counterparts. I loved Santana's "Soul Sacrifice" initially {I was stoned} but it never hit me subsequently like it did the first time I saw it. And I think the debut album closer is better. However, as a bonus track on the debut album on CD {or maybe it's Abraxas}, there's a song from Woodstock called "Fried Neckbones" or something like that. It's superb. I don't know why it wasn't on either of the first 2 albums.
Funnily enough, I always just barely tolerated Joe Cocker's Woodstock performance. It's one of those that has passed into legend, but leaves me thinking, "well, not all legends are great !"
I feel the same way about Ten Years After 's "Goin' Home." First time I saw it {I was stoned}, I thought it was out of this world. Every time subsequent, I marvel that I liked it because I think it's a boring song and a pretty tame performance.
Don't take the drugs, kids ! It distorts your perception of reality and makes you like Ten Years After then 10 years later you find you no longer do.