The anime is basically a punchline now (not undeservedly so), but I, too, watched it at the right time in my life to enjoy it. Definitely not one I’d rewatch, though. I think the main things with merit are the OP (which I still see talked about and covered all the time) and the opening sequence of the first episode (which I think was well executed for what it is).

Speaking of the OP, whenever Elfen Lied comes up I have to share this wonderful piano arrangement of Lilium by KenBan; the interplay between all the voices is exquisite. Sadly, the performance videos with and without sheet music got hit with a copyright claim, but I still have them downloaded; I’ve uploaded the 1080p version of the sheet music performance video here (link expires in 72 hours), but if anyone would like the 4K versions of either the sheet music video or the performance video (more camera angles, no sheet music) let me know and I can upload them! I also have the actual sheet music, which is no longer available for sale, and I’d be happy to upload that by request as well. Also definitely check out the rest of the channel–he does some wonderful performances and piano arrangements, with lots of Evangelion and Final Fantasy music in particular.