I did some OC time in the Littleton areas. Never had one interaction with law enforcement regarding it after living in the region for 7 months. If you want good NY style pizza in a place that is friendly to OC, southeast corner of Wadsworth and Bowles is a place called MC's Pizza.
This was taken there. Don't ask me why, but we all got together to take a photo AND DIDN'T THINK TO TURN TO THE SIDE TO ALLOW OUR PISTOLS TO BE IN THE PICTURE. (You can almost make out the Glock on the kneeling guys right side.) I'm still slapping my forehead on that one. The owner is an older Italian guy from Brooklyn who appreciated having good gun carriers in his business.
I also OC'd at the Red Robin just down the street from there as well. No complaints there, but I honestly don't believe anyone noticed, not even the waitress who bumped into my strong side while I was walking to the bathroom. OC'ed Wal-Mart at C-470 and Bowles during peak business ours on a weekend just before I was on my way out of state. I know people noticed there, but never an interaction and I was in the store for at least 10 minutes.
The only actual "surprise" OC interaction I had was while helping put a fence up with my roommate and another while at the apartment of this girl I had been dating, both the same day during election season. Both surprised parties were Obama campaign door knockers. The one at the girl's house I wanted to get rid of quick, he was interrupting us watching a movie. He wouldn't take no thanks as an answer so I came to the door right behind her and started engaging him in conversation. He saw the pistol and hurried through his talking points and left. The guy who interrupted me during the yard work asked my roommate if he was me. He said no and pointed to me carrying a few 2x8's. He saw the pistol and wouldn't stand any closer than 20 feet away and started his speech by saying, "Well, um... I used to be a Republican, but...". Kinda pompous and presumptuous if you ask me. He knows nothing about me other than I exercise at least one of my rights.
Enjoy your OCing in Littleton, it's nice.