Some of the abilities on Aghs are awesome.
Lifestealer's reversed eating looks great for some fun.Stupid amounts of life steal at basic level as well. Missing top! Oh damn.....
KotL's cooldown lowering may have vast implications on some characters.
Morphling+Chen+Doombringer=Permanent buffs and an army to go along with it. So many stupid things to do with morphling now. Io tele-link fun. Stun locks. Mega buff stacks. Just so cool now.
Enchantress being able to re-enchant stuff looks disturbingly good too. Never lose your nets or lightning or whirlwinds or buffs again. Unless you want to.
Heaps of damage/mana/cooldown buffs in the patch. Too many to list.....
Guardian Boots look nice. Can you activate them and a mek as well? Might go some way to alleviating all the extra damage floating around. Very expensive for support, but not terrible for others.
Increased heal/buff range up to 900 for all support items is handy for quality of life reasons. Support characters may have an easier time staying out of the way, because they're even squishier by comparison vs higher levels of damage.
16% miss chance on a Radiance at least gives it a reason to exist now. A little more versatile. Does it stack with uphill, spells and items?
Does Octarine Core fire spellvamp off Enchantress' Impetus? Handy anyway, but lifesteal pure damage might make it very buyable for her.
This may be the most mixed bag, nerfable patch yet! TI5 is going to be very different methinks as strategies get worked out.