My Jedi Guardian is now just a battle or two away from level 40. Been doing some PvP warzones with him, which was laughably bad at first as the other players were running circles around me. Getting better at it with each round, but a lot of room to go. Get decent experience out of running those, and access to good loot as you level up in Valor so I'd say it's worth it.
I also started a Smuggler and went with the Gunslinger advanced class, which gives him double pistols. Got him up to level 19 now.
It's interesting the dynamic between the two. The Guardian is basically a tank, but the Gunslinger is a ranged damage guy so the gameplay is a bit different.
Starting homeworlds were different, so the first 10 levels were no overlap at all. Since both were Republic, the second step was Coruscant, but even the mission overlap is interesting because the Gunslinger has different dialogue options. He pretty much flirts with any girl he runs into, lol.