Once you get past the mid-30s it seems you stop getting slotted gear as story and side quest rewards, so I often take boxes instead of commendations now if that is the only choice. Still, they use the same random loot tables seemingly, so there's every chance you'll end up with something useless.
On an unrelated note, I got an official email today congratulating me on getting my Sith Inquisitor to level 10 and giving me a link to a progression guide (which was pretty basic). I also levelled up a Bounty Hunter to level 10 (well both to 11 actually) 24 hours later, but haven't received any similar email for him. I wonder if it's just for the dress wearers. Maybe their metrics have indicated players of those classes need some extra hand holding. Here's the link they sent, if anyone is interested - http://www.swtor.com/progressionGuid...hInquisitor10/
Edit: One for the Bounty Hunter just turned up in my inbox. Based on that, it was simple enough to suss out the links for all classes: