Ranked in these QuestionsQuestion Ranking
Pro Simpler and cleaner than tmux or screen
Contains less code. Does not have to be backwards compatible. Two separate tools, each doing its job: session management may be used separately from tiling window/pane management.
Pro Intuitive/carefully chosen keyboard shortcuts
There are the 13 shortcuts that let you accomplish the vast majority of what you'll ever need (Mod is ctrl-g by default):
Mod-c to create a window, Mod-l/h to adjust window size, Mod-j/k to change window, Mod-n to select nth window in view, Mod-enter to swap with master window, Mod-space to change layout.
Mod-t n to tag a window with the nth tag (1..5), Mod-T n to add/remove tag n to/from the window, Mod-v to view all windows with tag n, Mod-V to add/remove all windows with tag n to/from view, Mod-0 to view all windows.
Pro Fairly feature-complete and stable
Con Not as widely/consistently available as similar tools
This isn't too unexpected since it's not as popular, but it can be annoying; even Ubuntu's repo version is 3 years out of date and lacks the tag features.
Con Not so actively developed
Even though other options don't see updates often as well. Despite this, it's fairly feature-complete and very stable.