I've found that a fair number of teams make use of first turn setup. That can be countered by using Fake Out + attacks on the would be set upers. And that in turn is countered by Quick Guard. So if you use a team like that, you should have Quick Guard. Otherwise they'll just take them out before you can get your set up going.
It's a bit of an edge case, but I'd say Quick Guard has its uses. Much more useful in triples though.
I use PokeGen to create legit hacks. I do not trade. I do not intentionally disconnect, ever.