Commando.....Is it good in PvE/leveling?
Commando does an excellent job of doing PvE and leveling and, if you don't want to run Gunnery, you can just do Assault Specialist for a different playstyle (it does slightly worse DPS than Gunnery, but it isn't just a lot of Grav Round spam with Full Auto and HiB breaks every once in a while).
Of course, I think it should be mentioned that there isn't really a class that *doesn't* level well, given the proper spec, especially if you've got a leveling buddy (which pretty much means that, as long as you don't double up tank or heals, you're golden). Even though Scoundrels do terrible DPS at 50 and are pretty much worthless except as healers, you can level quite happily as a Scrapper (this is what I did, even post nerf; it was genuinely fun and amusing mainly because your burst DPS was functional and useful because fights didn't last longer than 10 seconds). Commandos are terrible at PvP, but they're a great class to level (since they're the Repub class that gets their healer the earliest).
I had a lot of fun leveling my Commando as heals (Hammer shot is both a heal and an attack, not to mention you get all of the delicious Commando AoEs to make leveling a breeze). My Sage went up as the Balance hybrid which, while it was a lot of TkT spam, that wasn't *everything* about it: TkT is just your "basic" attack that you use while you're waiting for other abilities to get off of CD (Force in Balance), your DoTs to run out so that they need to be reapplied (Weaken Mind), and your procs to activate (Presence of Mind for instant Mind Crush or Disturbance). It should also be noted that, while leveling, a lot of the time you'll be using Forcequake to demolish entire packs of standards.