well, I have my 305x70x16 WildPeaks on for a few days now. Some views...
Very quiet on the road. I don't really hear any more road noise from the tires then I did with the stock 255x75x17 GoodYears. No rain yet. No off road yet... speeds up to 80 on highway, seems to run just fine.
My WildPeaks measure just a tad over 32" when mounted and with 30 PSI in them. I'm going to run for the week (through Wednesday) with 30 PSI and then lower to 28. Feels just a little firm then I would like over bumps, etc..
They are pretty heavy. This is my first Jeep, and my first really larger then your average tire size. These are heavy. I have MB 72 wheels (4.5 BS) and you also will need new tire snubbers before you mount the spare on the carrier. Everything I read on here says you should be OK on the carrier with the correct pressure on the tires via the snubbers, so I am waiting to mount the tire till they come in.
As for the speedo correction needed - I put these on and followed my wife in her JKU - hers has the stock (255x75x17) tires on and my speedo and hers were the same at 55 and 60 MPH. With that, I really don't think I need to do any speedo correction via the AEV ProCal. But, just to be safe, I did add in that I had 32" tires.
My MPG looks to have gone down on the dash from 19.2 to 17.8 on my commute - not bad for the difference in tires.