I've taken a 70-300 on every single hpliday for the last 8 years or so, never regretted it once. But I like that kind of focal length. Obvious good for wildlife but also makes for a good portrait lens at the wide end, great for landscapes, the tele end is also good for close to macro capabilities, all round still life, and even architecture. Most of my architecture shots are actually taken at fair long focal lengths because to shoot wider I generally find you need a PC/TS lens to control perspective. You can also get fairly good Bokeh out of them due to the focal length.
So it all depends on what you like to shoot but I find the 70-300 so versatile, and they are pretty light as well.
Some people would like nothing more than a fast prime attached to their camera for the whole holiday. I see the appeal if you shoot certain things, but those things don't appeal to me on holiday. I tend to shove a 35mm in the pack because it is small but I rarely take it out but it is nice to get a small light package. These days I am tending to take my DSLR with the longest lens suitable for the job (either 300mm f/4 with 1.4xTC or a 70-200mm f/2.8 or 70-300mm), and my Olympus Epm-2 with kit lens for casual modest wide to normal focal length shots.
If you use the 70-300mm a lot at home then there is a good chance you will want that focal length on holiday. If you rarely touch the lens but think there might be 1 or 2 opportunities then you need to think how important they are. Personally, I regret taking a load of lenses I never uses but I regret even more missing an opportunity because I don't have the lens. This is veyr true of wildlife photography , you can load up on your heaviest gear with heavy tripods etc and go trekking for 8 hrs and not take a single photo. But you never know what you will find, Some of my best photos have come when I was very close to leaving all the gear in the car.