I have had some degree of success with them in Z v P. Mainly i use them to defend against a 4 warp gate push as they just rip apart the gateway units so fast

i play in plat so im allright  and i like using armies of hyra lings, and it works pretty well

Hydras make someone like me, a Terran player who turns to air units when I see Roaches on the ground, a sad sad panda.

 @killroycantkill
Did you read the last line of his post he asked if anyone has had any success with hydras

hydra roach are great vs gateway units in zvp.
add corruptors when they get colossi. then tech to ultras.
 
don't use em in zvt.

If you're not using Hydra's you're crazy. They're the highest DPS unit in the game. They attack incredibly quickly and do a pretty good 12 damage a shot. They just need support that allows them to stand still and destroy stuff. A wall of Roaches or Zerglings works pretty well. 
Using an Infestor to Fungal a group of units and finishing with Hydras works good as well. Sometimes they even outrange the enemy whose Fungaled and can kill them without retaliation.
 
You should use them against a Protoss whose heavy on the Gateway units, Hydras own pretty much any Gateway unit without much trouble. They're only really vulnerable against Storm and Colossi.
 
And yes, they're slow, that's why you should spread your creep quickly if you want to use alot of Hydra's or use them defensively only.

And yes, they're slow, that's why you should spread your creep quickly if you want to use alot of Hydra's or use them defensively only. "

Gotta use creep
 
Just spread it generally and then when he pushes you can have hydras to rape him and then push the few extra feet to victory
 
Hydras are just extremely slow off creep

"don't use em in zvt. "

Hydras rape VRs like nothing else.  That alone makes them quite valuable.  

So so so very slow. 
 
They need a speed upgrade again.  I love hydras, and I mean, you might need a few in some situations, but right now, they're pretty much More mobile base defenses.

They're pretty crappy. They're meant to be a tier 1 unit and it shows. 
 
I still love roach/hydra though and try to do it as much as I can, just because I find it fun.

I use hydras almost exclusively against Protoss and often against Terran as well, and they perform very well for their price if you do not throw them away.  Don't attack-move with them or you'll throw away all the DPS the units behind the hydras in front could be dealing out, don't send them across the map to assault a base somewhere if you don't have a creep highway along their path, and don't run them into siege tanks.  Stimmed marines will eat them apart if they don't have something in front of them to soak up the damage, which is a good reason to produce roaches.  Marauders eat roaches apart, but do poorly against hydralisks.  Also remember to manually snipe the medivacs over the Terran's bioball before you attack move and spread the damage around.  Never mix them up with ultralisks as those units do not navigate around each other effectively and for the love of the Queen do not take them off of creep if there are psionic storms going down.

They work well against my void ray push -.-

" I use hydras almost exclusively against Protoss and often against Terran as well, and they perform very well for their price if you do not throw them away.  Don't attack-move with them or you'll throw away all the DPS the units behind the hydras in front could be dealing out, don't send them across the map to assault a base somewhere if you don't have a creep highway along their path, and don't run them into siege tanks.  Stimmed marines will eat them apart if they don't have something in front of them to soak up the damage, which is a good reason to produce roaches.  Marauders eat roaches apart, but do poorly against hydralisks.  Also remember to manually snipe the medivacs over the Terran's bioball before you attack move and spread the damage around.  Never mix them up with ultralisks as those units do not navigate around each other effectively and for the love of the Queen do not take them off of creep if there are psionic storms going down. "

Colossus are not amazing against roaches, or hydras mixed with lings, and you should have corruptors or mutalisks coming out in response to them well before your enemy gets enough of them to totally melt your hydras apart.  Psionic storm is devastating to everything in a zerg players arsenal and it's an issue you'll have to deal with using some serious micro whether you have hydras or otherwise.  Hydras at least have the DPS and range to pick off high templar before they fall even if they are caught in the storm.  With creep underneath them they can pull out of psi storms fairly quickly, but not without it. 
 
Hydras and roaches will utterly annihilate any gate army and stand up reasonably well to a gate army with a couple of collosus mixed into it.  Transition out of roach/hydra into hydra/mutalisks if you have the expansions available to handle it to secure air dominance and deter colossus and immortal overproduction and encourage stalker production, which are horrible against both mutalisks and hydralisks.  Hydralisks aren't mobile, which is the reason they aren't a win-button, but you can get around with nydus worms to protect expansions or harass the enemy base, as well as overlords if you have air control.

Hydras are good against protoss, they counter pretty much every gateway unit. They are very squishy, however, so you'll need roaches or at the very least lings to soak up damage while your hydras do work.
 
The reason you don't use hydras against terran is because you don't use roaches against terran. Marauders eat through roaches and hydras, so that wall of roaches that was supposed to be protecting your hydras falls fast, and you hydras go with them soon after.

Don't see why you would use hydras in TvZ even after the patch, even if they don't die to as fast to tanks.
Muta/ling/baneling into Ultra will prolly dominate that matchup from the Zerg side. 
 
Especially now that you won't be as forced to make roaches with the Reaper/Bunker nerf.

Hydras are great in ZvP (where you can get hydras and corrupters for the inevitable collosi), situational in ZvZ (hydraroach works well), and generally poor in ZvT. 
 
They are very very high dps, but quite squishy, so need other units to tank for them.  Also they really need you to be very proactive about expanding creep, or use nydus worms well to make them more mobile.  Hydras are a bit better against Terran now that siege tanks don't utterly dominate them, but they are still too iffy.  Against bio, marauders rape roaches so you can't go hydraroach to have tanks for the hydras.  Against mech, even though hydras are a bit better off, they still go down super fast to Thors, Hellions, or Tanks.  Against air, they'd be effective but I don't see too many Terrans mass air units for the most part.   
 
These days, hydraroach is probably my number 2 build against toss, it really depends what they are building.  I am lately really favouring mutaling against toss, cause it just gives you fantastic map control and can be very frustrating for a protoss player to deal with.