When patch 4.1 added the two troll instances to WoW's heroic pool, the newer, more challenging instances were separated in a different tier, with separate Valor point awards (much to the chagrin of people who wanted to get their weekly valor cap but who got tired of running those two zones repeatedly). Patch 4.3 adds three new instances, and these are indeed available as a separate category in the dungeon finder. What is gone is the additional Valor award.
You can now get seven VP grants per week (the last of which will be reduced from 150 to 100 due to the weekly cap), regardless of whether you take the option that only includes the new zones, or the other option (which includes all of the Cataclysm heroics you are eligible for, including the 4.1 and 4.3 instances). This makes for an interesting gamble on players' time versus reward ratios.
- The newer zones seem to be reasonably quick, drop better loot (until you have something better yet anyway) and have a higher starting item level requirement, which means that you're not going to be added to a group with people who have not done at least some dungeons in Cataclysm. However, the 4.3 zones are still a bit tougher than what you see in the old zones, so the chances - or at least the fear - of failure is potentially higher.
- If you go the unrestricted random route, the basic Cataclysm Heroics are going to be even quicker because players grossly outgear them, resulting in a high speed, low risk clear if those are chosen. However, you run the risk of drawing one of the new zones, or, worst of all, one of the time consuming and challenging troll heroics, which now no longer has any additional reward. I've seen a lot of people immediately drop groups upon zone-in, and I assume these folks were hoping for the easy win.
This is one of those times when I wish we could actually see the numbers. It would be fascinating to see which of the options players end up picking.