The battery is great as far as the quality and length of recording time etc. HOWEVER, this battery changed the shape of the camcorder (it sticks out the back of the camcorder significantly), so much so that my normal comfortable grip was made impossible to do because I coudn't rest my thumb flat across the back of the camcorder anymore. The camcorder is very nice, but this is a real bummer as I will now need to stock up on the smaller version of the battery. My hand is a male's medium hand with relatively short fingers, at least that's what my golf glove says.

I ordered this battery as a backup for my camera but it turned out the other way around. This battery last about 3 hours. Great for if you want to keep your camera on for extended events. This is not a knockoff brand. Its the real deal.

Is this Battery also good for Vixia HG20. I see it on Canon website it says it is compatible. Does anybody have any experience? Please help. Thanks.

Well, there's not really much to say other than it's a battery. No problems or anything with it. But you should be aware that this battery is thicker than the stock battery, at least for my Canon HF10 camcorder, so it sticks out further. Not really an issue for me, but if you have a camera bag that is already tight, you might have an issue.

I got the Canon battery because it will activate the battery-usage indicator in the camera and it will be able to be recharged while attached to the camera. I think the knock-off brands, though cheaper, aren't capable of doing these things.
Oh, it does increase shooting time by at least 2x.
Some days are diamonds, the next days is coal. But, life goes on.Canon BP-819 Lithium Ion Battery Pack for HF10 and HF100 Camcorders