I've taken three characters to level 50, two are in their mid 20s, while the rest are still somewhere in their capital worlds or have just left for the next planet.
With my main on the Republic side I've done a tonne of end game content from hard mode flashpoints to operations and dabbled in a bit of pvp/warzones.
Played with a hell of a lot of people from this forum and beyond through the class stories, general story, endgame, etc, etc, etc...
Taken on World Bosses with several different groups, shared in various events... most of which has been done on the Republic side so I still have a hell of a lot to do on the Imperial side.
Can't seem to get enough of the game since I've interacted with so many people and done so much but know that I've only skimmed the surface.