I brought a large box with a coffee maker in it once on Jet Blue. TSA had me go to the side and open the box and take everything out of the box for them. Other than that, I had no trouble with it as a carry on. . .
The TSA rarely enforces the 1 carry-on and one personal item rule that they have and almost never enforces any regulation on carry-on bag size. Some airline employees are more strict about the rules than others, so it's largely hit or miss if your items don't meet the published specs.
Since I started to bring my fishing pole with us to Aruba, I never had a issue with it, but the tackle bag is another story, which I pack in my checked bag. The pole, I carry it in a long case for for it and a backpack containing all my stuff, and its full...lol, and fits into the overhead. I've asked what it is and I tell them it's a fishing pole, no problem. I'll see how things turn out when I leave for Oregon, to go salmon fishing in a couple of weeks.