Here's my thoughts on the new jungle:
I feel that Maokai is stronger in this jungle relative to other junglers than he was in S3. The main changes that help him are the new shorter cooldown smite and the new slingshot xp mechanism. The change to bladed armor also favors him as it does a lot of damage to the larger monsters, allowing him to clean up the rest with his aoe damage. With my experience so far with maokai in the new jungle, I expect him to return to being a popular jungle pick as he was in Season 2.
Maokai's problem in the S3 jungle was single target damage, which was mostly a problem when smite wasn't up. But now that smite has such a short cooldown, you can use it every other camp, so his lack of single target damage becomes less of a problem. They also increased the hp of lesser wraiths which is a relative advantage for maokai as he has no trouble killing them whether they have 150 hp or 250.
The other thing about maokai is that he's an extremely gank heavy jungler, so in S3 he'd risk being be underleveled because he'd be ganking constantly and not farming so much, especially early game. This would also leave him vulnerable to control junglers who would counterjungle him, leaving him further underleveled. But now he won't be underleveled, because it's impossible to be underleveled as a jungler now due to bonus xp from killing higher level monsters. I mean, it would take some true dedication to shut someone down when you can level so quickly now if you're the lowest level person in the game. Due to the bonus xp from being underleveled in the jungle, by the time the late game teamfights start even if you had an awful start you're still only going to be one level lower than that control jungler who spent all his time invading you. In the new jungle, you can hit level 3 or 4 very quickly, then gank constantly for the next 3-4 minutes. Once your buffs come back up, you'll can catch up in levels naturally despite spending so much time ganking.
Unlike other junglers who's level 3 paths were slowed down by this patch, Maokai can still hit level 3 very quickly by blowing up the lesser wraiths on the way from red to blue.
Despite supports being so strong, Double Jungle is much better than before. Now that you get bonus xp for being behind in levels, and now that they added a the wight camp, it's much easier for two different people to get the amount of xp necessary to make double jungle work. I don't think this will see competitive play (hard to say, depends how much they nerf the support gold items...) because supports are so strong now, but double jungle is a lot better now than it has been in any other meta and it's really fun. At some point I may add a new section to this guide specifically for double-jungling.
I still build Jungle Maokai as mostly tank with 40% cdr. I don't usually build AP, although the new jungle gives more gold than before so sometimes you can afford Athene's or something if you have a few kills and you are already tanky enough. Mao has pretty good ratios. But full AP Jungle Maokai is too squishy to properly fulfill the role of tank/initiator, and sacrificing either cooldown reduction or tank stats for AP on jungle maokai is simply not worth it, so you need to get tanky first (get golem/locket or golem/Frozen Heart at minimum) before you even think about about building any AP. On the other hand, having high Cooldown Reduction is a must for Maokai as it allows him to chase better, peel better and spam his skills for more damage, making him a much more disruptive tank overall, with arcane smash every 3.6 seconds and twisted advance every 7.8.