Here are the facts: Smithing is [censored] easy to level up. Iron Daggers cost 1 Iron Ingot and 1 Leather Strap and increase your skill dramatically between all level ranges. With that in mind, you can then purchase around 20 iron Ingots for a really, really low price. Impatient? Fast travel or wait 48 hours for blacksmiths to restock. Rinse and repeat.
This, will ruin the game for you.
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If you want to enjoy Smithing, try this:
1. Don't. Fast. Travel. Enjoy the sites and mine your own veins! (Check out this mod; it's http://skyrimnexus.com/downloads/file.php?id=193).
2. Don't purchase Ingots or Ore(s) from merchants. Doing this will only kill the boner you get for your crafted goods.
3. Don't spam create Iron Daggers. Try role-playing and making 'sets' of armor for the market in the current city.
After restarting due to ruining it, I actually feel as if I
earned my armor/weapons.
I really advise you to give this a chance as I'm having a blast! Running around in Dwarven armor feels like an accomplishment at level 15 as opposed to the Legendary Daedric I had before. Haha.
Anyway, hope that will help you out.

EDIT: Oh! I forgot to actually answer your question. Doh. Smithing isn't overpowered by default. It only is if you exploit the [censored] out of it by mass-producing Iron Daggers at an early level providing you with high-level gear. This will only ruin your willingness to explore dungeons. Don't do it. Smithing can also be overpowered if you min/max your skills which I refuse to do (make alchemy potion.. enchant a set of armor with +enchanting.. make alchemy potion.. enchant a set of armor.. etc.)