I use Brizzly on a daily basis, but I might switch to the "new" Twitter. And I too wonder if they'll die off.

What I love that the new Twitter UI has: * infinite scroll * in-line media (embedded videos/images)

Why I might not make the switch yet: * their mute feature (useful when following someone who's tweeting way too much irrelevant stuff) * they crowd-source explanation of trending topics (offers a quick way to find out what's going on w/o doing a search)