Hmmm, maybe I'm in the minority here, but I don't like the Goblin Familiar much. He's ok, but not that great. Yes, he's cheap, but he has way more limitations than I think I'm comfortable with. He's very slow since he takes a full action to cast the conjurations and they have to be in his zone and he has no channeling trait. And, as Gwar pointed out, the Warlord is going to have mana issues due to the fact that he pays triple for Arcane spells (ouch), so the extra action(s) granted by this familiar are only so useful because I have the feeling that the Warlord will be mana starved.
Add in the fact that pretty much most conjurations that he can cast are Zone Exclusive and I think he will quickly run out of things to do. Repair conjurations? Blah. Are people really wasting a lot of time and effort attacking conjurations? It almost never happens in my games because it tends to be a HORRIBLE waste of resources. Sure, there are some new cards in this set that MAY make it economical to attack conjurations, but most of those will smash conjurations so quickly that one point of healing isn't going to help.
Sorry to be a downer on this one, but I don't think it's that great. Not useless and is probably worth throwing one in a build (maybe), but not that great. Least favorite familiar by far.
Now...can we see the Holy Mage Familiar please? Pretty, pretty please?