In Australia, a genuine NP-E3 battery is almost $300. That's a bit excessive for four AAs and some plastic casing. Given that you can get an almost identical third party battery for $35, choosing the third party option isn't that hard. (For anyone interested, I've found the ones from Aussie Battery to fit well and have a high shot capacity).
Although I've never had a problem, I am a bit more paranoid about the third party batteries. I charge them on a granite benchtop with nothing nearby that might catch fire. And I tend to check on them more regularly. I don't know if the instances of failure are higher than OEM, but there are enough stories to make you a little wary.