Ok, ok everyone has mentioned their chili-cheese dog and today I finally tried it. You're all right, it's delicious. The bun is split-top (New England) style and it's buttered and toasted (or grilled) perfectly. The American cheese under the very tasty dog was melty and delicious and the chili (beanless, like I like it on a dog) had a little bite and tasted quite a bit of tomato. I totally dug it.
I can't say that I like it better than my beloved Saints chili-cheese dog but I think if I had a few more from Guida's I could become a convert.
The waitstaff was very nice. I'd read comments elsewhere that indicated they could be surly but that wasn't my experience. They also have Giffords ice cream which I was too full to try but I've heard that it's excellent from a friend who frequents the Lakes Region of NH.