Have just installed the latest 0.5.12 now I'm writing this post from within Flock.
The automatic blog detection appears to be problematic, I did manual detection to connect to this blog. I'm not sure perhaps the prefix "www" is required.
The blogging interface appears to have greatly improved as I could select "source" or "editor", I prefer seeing the codes so I would normally click the tab "source" at the bottom.
Categories available are all shown but double clicking doesn't select anything? The entry for tags is easy just start typing and end each tag by a comma.