I mostly use gels and protein bars, but one thing I've really enjoyed is honey roasted peanuts. Light weight, you get some salt, some sugar, and a lot of protein/fat to keep you going. Also toyed with the idea of packing some coconut shavings or flakes. I've done dried mangos before, those are really good too. I don't believe in loading your body with junk food and only gels during a long run, but also haven't ran long enough distances to know if it makes a difference or not.
Hill intervals!? Holy hell, man. I'll do hills, I'll do intervals, but never both at the same time. That's intense.