The new jungle and jungle items are amazing. They make you think about which camps to smite how you can conserve your sustain and gives counter play. There is a somewhat limiting factor on champs who can currently clear but that can always be tweaked later.
On the PBE I have tried Jax, Sion Hecarim, Elise, Nocturne, WW, Diana, Nunu, Udyr, Skarner, Shaco and Nautilus. Out of all these the only hard clear was Nautilus. All of these champions had time to clear and time to gank sometimes even keep all mobs down while ganking. The sustain you get from the new jungler items is a bit lacking but overall the diversity is where it is at.
You can grab warrior enchant for those hard hitting champs like Sion or Hecarim. You can grab Juggernaut for those who need a bit of health like Skarner.(although I prefer this on SION and Hecarim but I usually play them tank.) The magus is a bit underwhelming but still gives ap jungles some love. And finally the Slayer enchant. This is a perfect item on jax nocturne and WW. Scaling att spd with on hit damage. I think I am in love.
The Smite options are also quite refreshing.
Stalkers give poor gankers a nice slow and some true damage.(I think this was made for Shyvana)
Poachers give a reduced CD on smite and increased gold for invaded jungle creeps.(Shaco Nunu Lee Sin all benefit.)
Rangers Trailblazer drastically helps some slower clearers with AOE smite.(Sejuani Naut)
Skirmishers is kinda a gank assist for those who already have sticking potential by giving a bit of damage on attack and vision when used on a player. (Xin Jarvan nocturne)
All in all I am very pleased with the thought put into this new jungle and with a bit of tweaks to some of the jungles this can be the best jungling season yet.