I'm a morning runner, just to put things in perspective. In general, if I'm doing a "shorter" run (fewer than five miles or so) I typically won't eat before heading out the door (unless I'm absolutely famished). Just a couple of glasses of water about a half hour before I plan to run, then a pit stop on the way out.
If I'm running "middle-distance" (six to eight miles for me) or longer, I'll usually eat a PowerBar Harvest or something along those lines 45 minutes to an hour ahead of time, in addition to the water. This is usually in the neighborhood of 250 calories. I let nature take its course so I manage a pit stop before I leave for my run.
On my "long" runs (10+ miles) I eat the same as for the middle-distance runs, plus I bring along some gels. I try to take them every 3 to 5 miles or so, depending on how I'm feeling. I also bring along 40 oz of electrolyte replacement drink (I prefer Nuun) or water (sometimes 20 oz of each).
If you do plan on eating before a run, it's a good idea to give yourself time to digest. When you're running (or engaging in any strenous physical activity), your body draws blood away from your digestive organs to supply more blood to the muscles. If you've got a gut full of food when that happens, you'll be pretty unhappy with this lump of partially-digested food just sitting there like a lump. No fun at all.
I would point out that gels are essentially Gatorade (or other carb-containing sports drink) in concentrated form. This is why it's imperative to wash down gels with water or other non-sugared drink to avoid gastrointestinal upset. That's to say that, for all practical purposes, Gatorade = gel. If gels are ridiculous for short distances, then so is Gatorade.
Mostly, experiment a bit and do what works for you. Every person responds to nutrition differently, so there's no one-size-fits-all approach.
Don
My Training Log
2009 Races
May 17 - Cleveland Marathon (3:58:39)
May 24 - Buffalo Marathon (4:12:19)
June 27 - UltimateXC Quebec Edition "Half Marathon" (~19.26 miles: 6:20:30)
November 22 - Philadelphia Half Marathon