Wow, ditto seems amazing now, especially as a revenge killer. People have said that it is especially good at revenge killing, but I think it can also switch in to good effect.
1. Against DD'ers, you can switch in as they dragon dance. The only thing is, they have to be going for +2/+2 or higher.
Turn one, they DD.
Turn two, you switch to ditto and they DD again.
Turn three, their speed is at x2, but your speed is at x2.25, so you outspeed them. Very risky, but it could work.
2. Well, a lot pokemon resist their stab moves, whether or not they are immune. And of course you might intimidate them. This might not be a good idea, though.
I can see boosting attackers falling in popularity. If you boost and they don't switch, you kill one pokemon and have to switch out of ditto. Double switches tricking ditto into a wall might be seen too. Ditto can be played around, but unless you can set up a sub somehow, not more than one pokemon swept per sweep!
Oh, and of course you can can set up with a ghost or psychic type, get a KO, be killed by ditto, and have a pursuit trapper fight back against a hopefully resisted (ghost) attack.