I bought a 12C about 4 mos ago, and I completely love it. I upgraded from a 997 TT and this car is in a different league. To answer your questions:

1. How much is the Iris panel upgrade? $4000. I got mine upgraded to IRIS2 for free because my car was under warranty and the IRIS1 screen was flickering.
2. How much is the power pump upgrade (I think it should be free). Unknown
3. How much are ownership costs per year? $1800 annual maintenance + tires
4. Any major faults or problems that anyone has experienced with their 12Cs yet? I had an intake hose come off during some spirited driving and the car wouldn't start. Easy fix.
5. Has anyone had any problems with vandals or other "haters?" I prefer the McLaren because of its supposedly lesser "recognition" and snob factor, in contrast to Italian makes. No problems with this. I get tons of "head turns", "thumbs ups" and "cool car" comments from people. The general public tends to really like my car. I don't get any negative reactions. A lot of curious people. But comments are always positive.
6. How much "attention" does the car realistically draw? I honestly don't care for attention; I'm buying the 12C for its engineering and ride comfort (yes, I'm sounding like an old fart), on top of its performance. I wouldn't mind the occasional dad coming over with his kid to gawk at it, but if it draws a crowd everywhere then it might become a bit annoying. See above. It gets a lot of attention. But mine is volcano red and really stands out in the sun. Don't buy a McLaren if you want to be anonymous.

Hope that helps.