I would say that the best you can get is about 300 shots out of a full battery charge with this camera, especially if you view the images after taking them. The battery, to me, is somewhat underpowered for what the camera is capable of in the level of performance. As with every camera you should always have a fully charged spare battery in your camera bag because they do have a habit of going out just when something important is coming up. I always carry one spare but in this case I will be getting a second spare battery very soon, especially if you are doing any traveling. Speaking of batteries, I would recommend using only the Canon battery for this or any Canon camera. The aftermarket brands may be cheaper but you don't know how the voltage levels in these cheapie batteries will affect the camera, now or later on during the life of the camera. And when you stop and think about it, the Canon battery is truly not that much more expensive when viewed over the entire life of the camera.
I hope this info helps you out! it is an awesome camera for the short money Best Buy wanted for it!