It's mostly the media/fanwork fandom side of LJ that got pulled into Tumblr.

It's great for sharing images and vids, but it's useless for conversation, imo, and there's nothing like LJ filter system for choosing who can see what you post or even to sort the posts you read by origin. :-(

To me it wouldn't be a great loss if it went away tomorrow, but until then it's a fairly harmless way of passing the time, and some people like the steam engine pictures I post.