The skill itself is not overpowered - how could it be? - but the rate at which it progresses seems to be a bit over the top, especially with the endless amounts of iron available for those with a bit of gold. My warrior spent one hour (in real life, that is) in Whiterun, hoarding and buying all the iron available in Whiterun. Every 48 hours I was able to get my hands on at least 5-15 iron ores and 20-60 iron ingots. Result: Near instant epic Smithing skill without ever having created something useful, rendering all but my not-so-precious dragon armor completely and utterly useless.
Now, what if a modder were to drastically reduce the amount of resources that vendors sell? Say, 1 to 3 pieces of iron ore and the same amount of ingots per vendor for every 48 hours, no more, no less. Perhaps even increase the price as well. That way, without abundant resources, you can't just spam the cheapest item 25,000 times in a row in order to become a master smith. You'd actually either have to go out and mine some of the stuff, or travel from city to city/wait 48 hours to stock up on every valuable piece of ore for sale. The latter option would be quite time-consuming and downright boring; this would make Mining even more useful, as you get free ore and nice views!
Yay or nay? Note: I'm not a modder, it's just an idea that came to mind whilst thinking of ways to balance out some of the easy-to-level skills.