What are some alternatives?
When comparing Open Tabs Next to Current and Simple Tab Groups, you can also consider the following products
Tabs Outliner - Next Generation Session, Windows, Tabs Manager and a TooManyTabs Solution That Really Works.
Session Box - Using websites with multiple accounts at the same time is made easy.
Simplified Tab Groups - This Firefox addon provides tab grouping features similar to the removed TabView/TabGroups/Panorama...
Tab Mix Plus - Tab Mix Plus enhances Firefox's tab browsing capabilities.
Conex - TabGroups married with Tab Containers and bookmark & history search
Tab Utilities - Tab Utilities is an ultimate tab solution for all kind of users who want to manage their tab, create multiple session and search for new tabs, etc.