From "Tools of the Trade", the original Artificer handbook by Ytterbium_Dragon upon whose work this wiki is based:
Want to be an arcane leader, but the bard's flavor is too weird? Or do you just want some extra controller on your leader? Maybe you loved your abjurer concept from 3.x, but had a hard time converting it to 4e. The Artificer is the answer in all of these circumstances. Artificer flavor defaults to being a magi-technical engineer, but their abilities can define many different kinds of flavor. They're the new quintessential transmuter, abjurer, or simple buff mage. Whatever your reason for signing up, you'll probably want to make sure that the character is effective.
Artificers are not just great leaders, they are incredibly flexible: you can summon, fight ranged or melee, have special familiars, act on other players' turns, and be proactive in your healing. At the paragon level you can buff other players (and yourself) through the roof or make other players attack while still keeping your attack.
HP - Right on par with other leaders. Better if you choose a Constitution-based build.
Surges - One less than most leaders, but Con builds will hardly notice
Proficiencies - Only the monk and rogue have worse weapon proficiencies. Your implements are decent, but you have to use them in conjunction with a weapon, which limits your weapon choice even more. Free leather armor is nice though.
Arcane Empowerment - A nice little perk. It generally won't amount to much, but it comes in handy.
Arcane Rejuvenation - Not too incredible all by itself, but it doesn't seem to take up one of your three class features, so why not? No way to break this one, but it's still a cool boost once in a while.
Ritual Casting - a free feat, and you get enchant/disenchant three and five levels earlier, respectively. Even at early levels you can ensure that your party gets the right gear.
Healing Infusion - Easily the best leader healing ability in the game. You get to pool your healing surges, and the first two heals of the day don't take up any surges at all. For better or worse, Artificers are stuck with Curative Admixture but can choose between Resistive Formula and Shielding Elixir.
Curative Admixture - Most leaders' healing powers restore surge value +1d6 hit points, averaging a bonus of 3.5. If you're using this power, you'll likely have a +3 or +4 Wisdom modifier, so the healing balances out. It gains +2 when other leader powers would gain +1d6, but hopefully you'll be increasing your Wisdom modifier to help it keep up. Overall, it's only slightly weaker than other leaders' healing powers, but that's greatly offset by your ability to use it to pool healing surges.
Resistive Formula - A proactive healing tool. This power is absolutely amazing if you know who to use it on. Healing in the form of temp HP prevents hp lost due to overflow, and it even grants a bonus to AC! In paragon tier, this power becomes absolutely obscene with Enhanced Resistive Formula. For optimal use of the power, have your ally trigger the temp HP just as the enemy hits so that the bulk of the attack is absorbed into the temp HP.
Shielding Elixir - If it were resist 5 all, this power would be worth looking at. Unfortunately, as of right now it's far too specific, causing it to be limited only to campaigns that throw copious amounts of mono-typed enemies at you (and even then you should think twice about taking it).