Pros
Works great for a quick and detailed overview of AUR and official Arch repo packages.
Sometimes one just wants quick access to information without the command line.
Cons
None.
Well not really a con, but when one has time to waste, the CLI is more interesting and can provide very specific details on anything package related. Go checkout all pacman's features and capabilities including makepkg, then there's expac, pacutils, pacman-contrib. . . . . . . . . .
[ $ pacman -Ql pacman | grep bin | basename-dr ]
makepkg,
makepkg-template,
pacman,
pacman-conf,
pacman-db-upgrade,
pacman-key,
repo-add,
repo-elephant,
repo-remove,
testpkg,
vercmp,
PkgBrowser