He got slightly buffed since he's a "mana hungry AOE jungler," all of which really benefit from the new spirit items.
Hecarim's whole point is an AOE DPS tank, like Amumu and Sejuani (and others). He's one of the most fearsome gankers because he can gank from almost every angle, and his movespeed means that even if he walks on a ward he'll get there in time anyway. The range on his ult is really strong.
In a teamfight, his whole point is to ult through their team (causing a fear to their whole team and is an incredibly strong engage) and then bruisering the ADC or APC. He lacks in enough CC to really do anything else, and that's the big reason he's not played much. If your team can't follow up on that type of kamikaze engage, you're done.
Triforce is core... it just fits really nicely. The 6% movespeed and the +20 movespeed on hit synergize so well with his kit, and the Sheen hits allow him to do ungodly amounts of damage because his Q is on a 2-3 second cooldown. Other really good items are Spirit Visage (lets his W heal for 24% of outgoing damage instead of 20%) and Randuin's Omen (give him some much-needed CC, and he naturally exists in the center of the enemy team so it works well.)