Pros :
- automatically save new tabs to (delete closed tabs from) current/active group (or workspace)
- switch group does not add new windows

Cons :
- cannot directly open a group in a new window. If you open a new window, you don't have access to your groups (you have to create a new set of groups for this particular window)
- switch groups reload all tabs (I know this is actually Firefox's fault), hope it will be corrected when Firefox allows hide tabs
- cannot re-order the groups, when you have many of them it can be annoying
- you cannot see the tabs in the "group view", so :
* you cannot choose the tab you want to go when you switch groups
* no delete tabs button (must open the group first)