I liked beta 1.7 PvP. There was no sprinting, and bows shot very quickly, making them incredibly viable if you had the resources to keep up your arrow supply. There was no food bar and if you had full diamond armour, there was no enchantment and you could jump into PvP knowing you had the best gear.
1.9's PvP is moving towards what would be expected of a modern game, dual wielding being something I have wanted to see for a long time, but dual wielding does not allow you to use the left click action on the offhand weapon, which means that dual wielding swords is not viable (which would be incredible) except for aesthetic purposes.
I want to see something akin to a dodge roll added, as this would allow for more dynamic fights, however this should be impossible to do with heavy armour, giving a tradeoff.
The glider item is cool, though using "Elytra" to refer to it I believe alienates people from something they would otherwise know immediately what it is. It's nice to have it in the game, though, similar to Guild Wars 2's Heart of Thorns expansion.
I'd like to see more abilities or combos which would allow for more experimentation and learning in PvP.
The best thing in Minecraft 1.9 in my opinion is the addition of the vast array of new NBT tags, and other item properties that lend themselves to an official API. Although it's become almost Half-Life-esque in the way that it has been promised for years and everyone has started to lose hope, I believe there have been significant steps taken towards this. Once this is released I think some of the remaining Minecraft modding community might be salvaged.