As a chronic die hard multiple tabs opener, Onetab litteraly made my browser usage livable.
It saved me several times, having hundreds and hundreds of tabs open and can't be simply closed.
I use it daily.
OneTab allows me to continue hoarding tabs, but also make sure they aren't causing my browser to come to a standstill or get over-cluttered. When I send a group of tabs to OneTab, I try to make sure they represent a project or task I'm trying to accomplish instead of just blasting everything away. This makes it really easy to pick up a project if it comes back to the forefront of my tasks. Otherwise, if it ages there too long, I just get rid of the whole group.
