It's all about maximizing the boosts you get (in Stats, Armor/Damage, etc.). Commendations can always get you some useful and very good stuff, and can be especially useful to get good mods if you have the customizable (Orange) gear. BUT, if you are offered an item that is compatible with your character class (e.g., boosts Strength if you're a Jedi Knight, Cunning if you're a smuggler, etc.) and it's more than 4 levels higher than what you're currently using, it's probably a good idea to pick it. I also like to keep my Companions pretty well-geared up, but that's because I like to do most of my stuff single player and having a strong companion is more useful to me more often than having a characters who's got just a few more good gear items. If the boost is a non-essential Ability (there are many other threads on that topic here), stay away from it. But otherwise, I just compare the level of what I have and what I'm being offered and use that as my guide.

This may be a totally dumb question, but I thought Light and Dark didn't cancel each other out, in terms of weapons req purposes? Did Bioware change that? Your overall alignment shifts, but you can be "Light 2" and "Dark 3" at the same time, can't you? DId that change in 1.2?