I am going to try to shift away from Twitter and Tumblr and back to LiveJournal. Twitter is still good for quick, pithy one-liners (like the "chilly verde" joke I just posted), but trying to converse or compress complex thoughts into 140 characters is inane.
Tumblr ... as prickvixen said the other day, I dislike having to rebroadcast something if I want to comment on it. Discourse in a Tumblr thread is just not easily accomplished.
And yes, I still have a blogspot blog, but you know what? Never really used it that much, and now it's largely obsolete in and of itself.
I like LJ. I am comfortable here, and the interface is solid, time-tested, and lends itself to narrative and discussion far better than other platforms.
Twitter will still see use -- I do toss out occasional Twitworthy one-liners that aren't compromised by the enforced brevity, and LJ retweets my journal entries automatically, giving them exposure even to the crowd that abandoned ship long ago.
I'll still use Tumblr, as well. There IS a community there, and I'm part of it. Most of my tumblr entries will just be repost/links to relevant LJ entries, however.
I've got an LJ app on my phone -- guess how I'm typing this now? -- so really, it's as accessible and convenient as any of the hip, happening flavors of the month.