Really good extension. I miss a few thing from New Xkit (like the extension to filter the mass post editor), but for what it is and what it promises, it's amazing! I'm particularly surprised by how fast the Show Originals feature works. I'm not removing New Xkit yet, but this extension motivated me to disable it until I need it.
Tumblr's mass post editor is still built on legacy code, so XKit Rewritten has no need (or abiity, as of now) to target it. Glad to hear you are enjoying the experience so far!
