BarTab migrated into Firefox! Rated 5 out of 5 stars
The most convincing proof of the greatness of this idea is that BarTab functionality migrated into Firefox.
Since Firefox version 4, you could set browser.sessionstore.max_concurrent_tabs to 0, and you would essentially have a built-in BarTab (or you can use BarTab Lite).
Starting with the Firefox 8 the new preference is called browser.sessionstore.restore_on_demand (set it to true). Moreover this preference is exposed to user!
====> Go to Preferences/Options dialog => General and enable checkbox "Don't load tabs until selected". <====
Don't wait new versions of BarTab anymore!