Tumblr is great for running across the most wonderful or beautiful or humorous images, and being able to quickly bounce them along to your own followers. (I've been making a lot more icons in recent months, simply due to the increase in acquisition of striking pictures.) It's terrible for holding on a conversation (because every bloody reply appears to all your followers as a separate post, whether they're interested in following the discussion or not) -- definitely keep a foothold on LJ. Also, looking into browser extensions like Missing e and Tumblr Saviour -- the latter trained me into tagging my own posts more frequently, just knowing how annoying it is for the people who follow me but aren't interested in being spammed with pictures of that one person or whatever.