I recently had to purchase a few camera batteries for my Olympus E-3 SLR Digital Camera. I have six batteries in all for my camera, and a few of my previous batteries were not the Olympus brand but a compatible battery. They stopped working for me after about a year of use. They charge and will power my LCD screen, but they will not allow me to take photos. My Olympus brand batteries have been holding up well.
So I decided to purchase four more Olympus brand batteries, specifically made for my camera. I was able to get a great deal on them at Amazon.com, $39.95 for each battery. These batteries, once charged, give me hours of use before they require charging again. And I know they are good batteries, because the ones I purchased that were not the Olympus brand are already shot, and my Olympus batteries are still good. I use two batteries in my camera's battery grip to power my camera, and I have six batteries in all. This way, if I'm on a photo shot and I'm taking a lot of photos, I have extra batteries to fall back on. But I have found that I don't often have to change the batteries. They allow me to take a lot of photos before they need to be charged again.
I am very well pleased with the Olympus brand BLM-1 Li-ion battery. I will not be using any other compatible brand for my SLR camera.