i find hordes interesting, good chances of experience, finding wild held ítems (i.e horde of pikachu), shiny pokemon, EV training, etc. On a side note, with that horde of tauros with the miltank in the trailer made me wonder if they will finally make miltank be able to produce both tauros and miltanks eggs at least with a requirement of putting a tauros and a miltank in the day care.
Going back to hordes: I think all the abilities of the pokemon will be activated at once like in double battles and you will be forced sometimes to switch pokemon, but considering the fact of training weaker pokemon without exp. share, you will most of the time switch the in-training pokemon with the strongest pokemon in your party or the one that has the best type advantage to resist the attack, of course it would mean a turn lost and recieving 5 attacks (this makes me remember some games where you get ambushed and the enemy wild team get the first turn). Ofcourse, more pokemon, more challenges. For those hordes where all pokemon have sturdy, the most possible solution would be a moldbreaker pokemon that can hit multiple targets, so i wonder if they will add a pokemon with that ability early in game and allow it to learn multi target moves.