Yes. Item choices and clear speeds in particular.
Well, then let me preface this by saying that what I'm about to say is just my own thoughts after some experimenting on the PBE. Also, when I say I feel a champion is better/worse, it's in relation to how I think other champions will do in S5 and not whether they're better than in S4.
Diana
Much better. Diana's issues in S4 is that 90% of the time needs level 6 in order to gank unless the target is ridiculously overextended when she has red buff. This gives her a hard time against early gankers like Lee, Kha, Panth, etc. who can get their team rolling. S5 mitigates this by A.) making level 3 ganks more difficult to pull off and less frequent and B.) reducing the time necessary to reach level 6. Her clear speed and sustain are quite good. On top of this, the new AP jungle enchantment (90 AP, 10% CDR, MPen) fits her perfectly. Not only does this item not need stacks like SotSW but the stats are overall better. In S4 she's fringe viable in solo queue. I suspect she might become a real alternative to Fiddlesticks for teams needing solid magic out the jungle.
Volibear
Slightly worse, possibly unchanged, possibly better. I know it's a cop-out answer, but I'm having a tough time getting a read on how he'll do. On the one hand he's currently played as an early ganker and that's been hit. His ult is nice and all, but it's not a massive boost to his ganks, so hitting 6 earlier isn't a huge change on him. That said, counterjungling will be more important and Voli is undervalued in that aspect, just no one does it because he's better off ganking in S4. What he loses in ganking power he might gain as a counterjungler. Doesn't seem to benefit from any item change. His clear relative to other champions is average. Sustain is good but in my experience he couldn't do a straight level 4 clear because he ended up frequently triggering his passive by accident.
Sejuani
Better. I'm not a fan of S4 Sejuani jungle because it takes up to level 7 before she can sustain well, so I didn't get my hopes up in the harder jungle. Shockingly, she's just peachy. For reasons I don't understand I actually feel like she sustains better (pretty sure it's because of the flat hp/mana regen) than in S4, relative to other champs. Clear speed is solid. Faster access to level 6, though not needed. She has decent hp left after a level 3 clear for ganks and has a really nice level 4 gank path. I had the best success running armor reds-armor yellows-MR/CDR blues-HP quints when clearing. Item changes don't affect her much, although if you happen to get fed early on the AP enchant ain't half bad if you want to get cheeky. Also, and this is a general comment for all junglers, I don't know whether or not finishing your jungle item ASAP is 100% necessary now. Sure, they're all very cost effective once you take into account that you need to buy a machete upgrade anyways, but without the gold generation incentive it might be reasonable to do something like upgrade machete->boots->RoA->enchant jungle item.
Tryndamere
No clue. Rule of thumb, where you jungler is now relative to others is close to where he'll be after. I don't play Tryn, but I suppose he likes the AoE smite upgrade for faster clearing and both the new AD/LS and ASPD/on-hit enchants? Yeah, no clue.
Brand
Stahp. Just, stahp. Actually, no idea. My own feeling is all the super fringe ranged AD and AP carry junglers are going to have a rough time. Not only is the new jungle not friendly to squishies as it is, but leashes aren't going to be a good either because of the initial spawn timers. Never bothered trying stuff like Twitch, Jinx, Lissandra, or Karma.
EDIT: lol, I just wasted 30 mins at work writing this. God bless professional desk employment.