The benefits of watering slowly are to avoid 'dry pockets' in your soil.
If you dump water on top as fast as you can it will create channels in your soil. Water takes the path of least resistance, just like water carves streams out of bed rock.
Usually if you water slowly for the first 1-2 weeks(and for the first 1-2 weeks each time you pot up) it conditions your soil and you can water more evenly, much faster without creating pockets.
I've seen plants pulled out of soil where there was dry spots in the medium, and no roots grew there. They weren't big, but there was a handful of them in the 5 gals of medium, maybe golf ball size. I bet there was 1/2-1 gallon of soil with very little root development, essentially wasting that much space. Why plant in 5 gal container if your roots are only able to take up 4 gals of it because of dry pockets?
I think bottom feeding actually helps condition the soil to wick water up evenly, like a sponge. Another reason I believe, IMHO, people that water from the bottom swear by it's effectiveness.
I think it's good to water slow, but you don't need to water THAT slow. If your growing in a 5 gal container, split your water into 3 doses and give yourself a couple mins inbetween each dose. This is more then adequate.