Like other comments, I don't need to reload or log out my gnome shell when adding an extension.
But it's true that I used Shell only for the last 6 months, so I'm not really aware of the broken extension problem, but it's clear that it can be a huge probleme, especially because even though Shell is good, it misses some things out of the box that are really useful, like I said in my blog post.
What distro are you running Gnome on? I ran 3.6 on Archlinux and some extensions didn't come up automatically. For example, the gnome-shell-system-monitor doesn't apply changes without log-out (I am not sure about reload, never tried that).