Okay, here goes...
Siri: I've heard that the issue is that the microphone in the iPad 2 isn't good enough to support Siri. Now, I find this a little hard to swallow, as I used to use the original Siri on my iPad and never had a problem with it. Also, I've tested using Dragon Speech to Text on my iPad in a crowded restaurant, and it got almost everything I said (while my dad's "dumb" phone's voice dialing feature couldn't get a single name right in the same setting).
Performance: I would tend to agree that iOS 6 should perform fine on an iPad 2. The only significant change in the hardware between the iPad 2 and 3 was the GPU for driving the retina display, IIRC. And as others have pointed out, the iPhone 4s is on essentially the same hardware platform, too.
APIs for better gaming: Huh. That's cool, I guess. But it really doesn't effect me that much. My iPad is a work tool, an Internet portal, an ebook reader, and, sometimes, a movie player. When I do play games, they tend to be simple little time wasters, or the occasional logic puzzle based game. So, at least based on the example you offered, I don't see that this is all that interesting to me.
Big thing for me: As I use my iPad as a work tool, it's valuable for me to be able to move files around a little more freely than iOS natively likes to let you. For this reason, from the time I was able to, I've kept my iPad jailbroken simply to have iFile installed. With iFile, a camera connector kit and a USB SD card reader, I can copy files from my iPad to an SD card and hand the card and reader to someone else for loading onto their system,or vice versa.
When iOS 5 came out, there were sufficient improvements that I chose to upgrade even before the jailbreak was available. For that time, I dealt with less effective work-arounds to do the things that I wanted to do, but I was happy when the jailbreak became available. And now I'm just trying to assertain whether or not iOS 6 has the same temptation value.
Thus far, the answer seems to be a resounding "no".
(The only thing that comes close is the turn-by-turn navigation that's built into the maps app. But, as someone with a good sense of direction who is quite adept at reading maps, this is hardly a pressing need.)
