I used to have a few favourite hills. They were named the mini and major FOff hills because that's what my training partners said when we ran up there for the first time 

The mini was the mini because it was shorter but it made up a good workout because it was steep and got steeper in the last 15 metres. We used to run at about 75-80 % intensity up to the point where it became steeper and then really try to push out the last 15 m as hard as possible. It was only about 50 m in total but do 6 properly with a good warm up and cool down and you're legs are jelly!

I had large quads when I was doing this but I think while I was very strong at running hills my legs were not strong past the range of motion I used for running. Also my hamstrings were no where near as strong which might have partially contributed to the knee injury I ended up with.

So I'd say go for it because it gives you a lot of power and normal hills during a run will become old friends you use to drop people you're running against but also do other balancing exercises like a lot of stretching and plenty to strengthen the hamstrings, maybe a little bit of backwards running (on a grass oval without any obstacles immediately behind you )

I guess after reading Scraps post I should clarify that it's good for a runner who might encounter hills in a race they might be planning and since I know you're thinking marathon I can see they might be relevant to you. However, I can't say that it helped my boxing in any obvious way that I couldn't achieve from doing sprints on the flat.

In boxing I think it's always my arms that get tired first too so to achieve mental toughness and pushing through pain for boxing maybe it's not as relevant as pushups or hard bag work or just intense sparring. It does teach you to run hard on hills though which seems to be something many people can't do in running events.