I just did this, and thanks to this thread and a couple others, didn't break anything except for the bits I meant to break. I drove her around for an hour, checked for codes, and it looks like it really helped!
As the OP said (and I have disagreed with some of the OP's claims in the past), the hemi idles smoother and accelerates with much less hesitation. Moreover, when I checked for codes I noticed that a nagging P-code for incorrect oil viscosity had cleared.
Here are my tips:
1. Plan on breaking BOTH tabs. The sensor needs to rotate just past 90 degrees to clear its internal threading, and life is just too short to fight with the little tab. It doesn't need to be a clean break because the sensor will have risen up on its threading. As said, a little pry with a screwdriver will do it.
2. My experience was 100% curse-free, which really scared me once I had finished. What was it I had forgotten? Apparently nothing. And believe me I've got huge hands, and the dexterity of an angry elephant. If I could do it anyone can!
3. Take some time to scout out the workplace. The pix in this thread REALLY helped, as well as everybody ranting about what an asterisked-up task it was. I went slowly and was done in twenty minutes, and all but 30 seconds was spent going "really? really?" until I'd gotten the courage up to go ahead and break the back tab.
4. Once you find the tabs, carefully lift the vacuum hose up and over the tabs before you got at them. The back tab is fairly high, maybe 2 inches, which isn't clear in the pix. I went at it from the Passenger side, using a long screwdriver to lead the sensor around. The tab broke just under the screwdriver.
5. Once I'd broken the first tab, I lowered the hose down below the snsor so I could rotate it and see that the other tab had to go, or else my sanity would. Once that tab was broken the thing popped out like a used gerbil, and it was easy enough to replace.
I haven't driven enough to give an MPG report, but over the last month I'd noticed my mpg's falling, and wasn't sure if the dealer had messed something up. Finding the oil visc code only raised the paranoia level. But as I said, I noticed IMMEDIATE benefits, and I am optimistic regarding mpg's. We'll see!