Well, I'm support bot and whenever the other bot lane doesn't have flash, it's a guaranteed first blood for us. Every single time, unless they get off a good exhaust. But if we have a ganker come around behind, we kill them anyway with our exhaust. If they don't have cleanse, they'll get raped all day and all it will do later on is negate a single CC spell in teamfights, while we have over-wall escapes and the element of surprise and easier buff, dragon and baron steals not to mention better ganks than they can ever get unless you triple tower dive on one person with whatever inferior summoner spell you're using.
I used to hate it, too, when I didn't use it. Back before 30 that is.