I used to use the Energizer rechargeables in everything. I had the charger with the fan in it. About a week after I bought my 580exii, one of them leaked all over inside it. It still works (fortunately), but I threw every rechargeable battery I had away. Double A's are dirt cheap if you buy a 36 pack, and they last a lot longer. I'll never use the expensive rechargeables again.
Bummer about the leak, but I trust you're aware that regular old AA batteries can leak, too. IMO, the main advantage of the NiMH rechargeables isn't the long-term cost savings or the environmental benefit of generating less waste. The lower resistance of the NiMH chemistry means the flash recycles twice as fast as with alkaline AA batteries - and that's a huge advantage.
I've never had a rechargable battery leak, and i've had hundreds of them. A battery may have been damaged from fast charging or discharging, the pressure builds up when they get hot.
On the other hand, I've had almost every brand of alkaline batteries, and all of them will leak if left in the equipment too long. They are a real problem if they are older batteries. I've bought batteries 1500 at a time for use in my business, and once they are near the expiry date, they can leak at any time.