Not mentioned in its own thread; Tumblr recently relaxed (but did not eliminate) some of its nudity guidelines very recently (the imposition of which had negatively hurt the site's engagement to say the least). Seems they're really flirting with their old user base. Some comments on this talk about zero days/session stealing being a problem.
Tumblr has been my favorite social medium for a while now, for many of the reasons mentioned here, but it is <i>not</i> a replacement for Twitter. It's oriented toward longer posts, which among other things means that you usually won't be able to see multiple posts on screen at once. In fact, the "color of the sky" post was a deliberate prank on this; it's very very long, to make it even harder to get to the next posts by scrolling (avoidable using hotkeys though). Reblogs are similar to retweets, but seeing all replies to a post at once is nowhere near as easy as on Twitter. The UX is just very different.<p>Most importantly, the people there don't <i>want</i> a Twitter vibe. (That includes me even though I'm also on Twitter and in fact have far more followers there.) They have their own vibe. Skews young, <i>stridently</i> LGBTQ- and ND-friendly (plus fandoms which were already mentioned), a bit too much "armchair socialism" even for me (and I'm pretty far left). People there are genuinely curious, not just "curious" enough to mine others' posts for points to pick at. Shitposting and trolling are welcome as long as they're funny, though there are plenty of longer and more thoughtful posts too.<p>Overall I find the experience there very pleasant, but people who are less aligned with the local aesthetic are definitely not going to have a good time. Since there's very little technical/business discussion, and even less of the "fight club" atmosphere that prevails here, if you're reading this I'd say you should probably find something else.