Motorola

I have a fairly new battery in my RAZR V3m but due to heavy use I have to charge it nearly every evening. I see a lot of non-OEM extended batteries with the door for the RAZR for sale on eBay and all of them say something like, "This battery is made specifically for your cellular phone and to meet or exceed the original manufacturer specifications."

I'm definitely going to get the extended battery although I can see from the photos that my phone will no longer fit in my case. But I'm wondering if the non-OEM battery is indeed as good as the genuine Motorola.