don't know why this post lists me as 'MikeFusionH' but i am the original OP (mmtphoto) so this is weird-anyway thought I'd do a follow up-
I drove this car with the cleaned O2 sensor for about 2400 miles, and had to clear a CEL light probably 3 times so I got a new sensor and no more issues. it seemed to run smoother and gas mileage was marginally improved. shortly after replacing it, my wife had an issue on the interstate where the car lost power and the 'wrench' light came on indicating limp mode. she called and i told her to get to the side of the road and shut it down and restart it. she drove it home and we left it sitting while i could scan it to see what was up-no codes, so on investigating i found that the throttle body was the probable cause of this problem. this 2010 has about 118,000 miles and i always periodically clean the throttle body, but the consensus was that the oem throttle body was defective. i found one on line for about $60 and a gasket for $12, installed it (15 minutes total if that). I disconnected the neg cable and attached a jumper from the loose ground to the pos cable to power down the system, started it up and let it idle for 10 minutes with the ac running. then i drove it gently for another 20 minutes. finally i did a HVB balance using my scanner. the removed throttle body was clean on top but the bottom of the throttle plate was nasty. these changes (new O2 sensor, throttle body, reset computer and rebalance of the HVB) now gets gas mileage up to close to 40 mpg as opposed to the 35 mpg it was getting. So other than oil changes, these repairs and doing the rear brakes at 94,000 miles this car is still stock and gets 40 mpg, is full sized, and looks/runs great.
the ni-mh batteries after balance were within .01 volt and it still has great performance in HV and ICE modes. Love this car and hope to get more years out of it plus I might consider, when the time comes, getting a new battery pack just to drive it more years. Ford hit a home run with these cars IMO.