It's a common complaint that level 70 epics are too marginal of upgrades over dungeon blues; heck, I've even kept some quest reward greens over Karazhan epics. It looks like a lot of that is set to change with patch 2.1. According to reports from the PTRs almost every 70 epic has had its stats buffed in tonight's PTR patch, and fairly considerably, too. World of Raids is reporting that Tier 4 gear has had its item level ("ilvl" for short) bumped from the current 105 up to 120; Tier 5 has gone from 120 to 133; and the rest of the epic loot has been increased a corresponding degree -- T4-level stuff has gone up by 15 ilvls, and T5-level stuff by 13.
What's all this ilvl nonsense, you ask? Well, the math is pretty complicated (1.5th roots are involved), but in short, ilvl represents how "good" an item is. An item's equip level
is used to be determined by its ilvl, back before BC (specifically, it was ilvl minus 5, with a cap at 60), but other than that there's no way to directly see ilvl in the default UI (mods can show it). Items that are supposed to be comparable have the same ilvl: all T4 gear has the same ilvl, every Jazeraint Helm, regardless of suffix, has the same ilvl, and so forth. That is all to say, ilvl is a way of measuring "how much" stats a piece of gear has. For more details on ilvl calculation, see the WoWWiki page on the subject.
So, getting back to the subject at hand: level 70 epics are getting better. Their ilvls are getting boosted, which means they get to have more stats. And for examples of specifics, head over to World of Raids, where they're keeping a constantly updated directory full of new item tooltips, in alphabetical order. Edit: MMO-Champion also has a very good listing of new stats. There are also a few reagent changes for some craftables. World of Raids reports:
Blacksmith changes (5-7-07)
- Tier 3 weapons require 5 nether vortex.
- Tier 2 weapons require 8 primal nethers.
Engineering changes (5-7-07)
- Goggles now require a primal nether.
(Image courtesy of the International Mountain Bicycling Association)