In an interview on Gameplanet, Ghostcrawler talks about reforging:
The way [reforging] works is, instead of being tied to trade skills, now there are NPCs in the major cities. You go to this NPC and tell them you want to reforge an item. The interface opens and you place the item in it. It then asks you to pick a stat to reduce, and then pick a stat to add. You can’t use primary stats like agility, strength and intellect, but you can use all of the secondary stats like hit, crit, haste, parry, dodge, things like that. Then you reduce one of the stats by – at the moment it’s 40% but to make the example easier, say it’s 50%. If you have 100 crit, you reduce that by 50, that then gives you 50 points to put on, say, hit. And the cost of that transaction is the vendor cost of the item, so if you later decide to sell that item, you’re not really out of pocket.
I have to say that I thought reforging was going to be something you did rarely, to get rid of excess hit or a really bad stat. But from this description, it seems like reforging will be something that you do to every piece of gear.
To see what I mean, let's use our old technique of assigning a dollar value to stats. The standard 4-stat item has 2 primary stats and 2 secondary stats. We'll just ignore the primary stats because they don't change during reforging.
Let's assume, that for our class:
1 Crit rating = $1.00
1 Haste rating = $1.10
[Item with Crit and Haste]
100 Crit rating = $100
100 Haste rating = $110
Total = $210
Then we reforge some of that crit into haste.
50 Crit rating = $50
150 Haste rating = $165
Total = $215
Reforging the lower value stat into the higher value stat always makes the item better. So whenever you get an item, the first thing you do is reforge the lower value secondary stats into whatever secondary stat has the highest value for your class.
Pretty much the only time you wouldn't do this is if you are hovering around an inflection point in the value of a stat, such as the hit cap. At that point you get to bust out the spreadsheet to see if reforging is a gain or a loss.
Now, if you can't increase a stat that already exists on an item, then items with the two best secondary stats won't be reforged, but all other ones will.
I guess I understand the impetus behind reforging. My paladin has an i264 2H weapon, which I would like to use for Retribution, but I can't use it because it puts me 3% over the hit cap. However, I can't help but wonder if the implementation as described will just lead to an extra layer of complexity. You get a new piece of gear, and you have to reforge, gem, and enchant it before you can actually use it. Sometimes, I miss getting a new item and being able to equip it immediately.
Not to mention that there's a possibility for unintentional power inflation, as every item will contribute more than the design on paper, and maybe a lot more if a specific secondary stat turns out to be much more valuable than the others for a specific class. With both reforging and gemming, a character could focus a huge amount of her equipment budget on one specific stat.