Gels

I'm more interested in whether keytones have any value for the marathon and if so, how to take them.

Beer drinker wrote:

Is there any benefit to taking a gel before a race (during warm up)?

For a marathon, getting the gel at least partially digested before you're dealing with the physical stress of racing is a good idea. Also, if you're relying on the gel for caffeine intake, your body needs even more time to process the caffeine. Optimal timing is dependent on a lot of things, but the idea itself isn't crazy. I doubt it's critical, though.

The Gel makers recommend this. Is it better to wait for a few miles?

Probably not better, but if that's what works best for you, no reason not to wait until you're a few miles in. Experiment and see.

Is there any point in taking gels for short races 10K, 1/2 marathon etc?

It's better than racing in a fasted state, but oatmeal or toast+jam is cheaper and doesn't taste like glue. Getting some carbs in your mouth during the race might marginally improve performance, but a cup of Gatorade is cheaper and usually more readily available. But in terms of fuel, no, you don't need anything to run your best race for anything under 2 hours, and you'll waste time and energy trying to swallow and digest the gel and risk choking/coughing.

The only time I would take gels would be in a marathon race until about 22-23 miles.