I’ve had qualified success using it. The complaints are totally fair, it’s slow to load, incomplete, and while it preserves snapshots of individual sites, it doesn’t preserve the entirety of what they link too.
But it’s great for finding otherwise lost little bits of information. In fact, one of my first posts here (rather than just lurking sans account) was because of memories I eventually recovered with the Wayback Machine.
NOTE that if you go to the SD site these days, it’s still missing the last section, and attributes the whole thing to Cecil despite being only Dex’s segment!
Anyway, I also wanted to say archive.org is far more than just the wayback machine, with audio, visual, “print” and software stored from times otherwise lost. I’ve played Oregan Trail, found old radio dramas, and picked up audiobooks of classic works.
YES, the interface is positively reminiscent of the 80s, and the search is in desperate need of updates, but I consider the whole thing like going to a good used book store. The organization may be haphazard, and they are likely to be missing much of what you want, but what you can find you likely wouldn’t find anywhere else!