Camelot
Adventurer
I love the mechanics, which give it a very unique feel compared to the other leaders. Healing Infusion as a healing mechanic is very different from any other healing mechanic out there.
It would be nice to see them gain a larger power selection, though. There are more than a few levels which have encounter powers that are actually worse than Magic Weapon, or so similar to it that their value is questionable.
I agree with this 100%, and it's worth repeating. The artificer is awesome because it feels so different from your standard leader. As an artificer, you lead through your allies' magic items. You have so much versatility you won't know what to do with it (I'm exaggerating, you will know what to do with it; you'll have the right thing for every situation). Your allies will love you, because you can evenly spread out the healing surges of the party, instead of having the fighter run out while the wizard is still full. And the flavor is so unique! I love artificers.