How much user available space left in iphone 4s 8 GB after latest iOS 8 beta update?

And does iOS 8 slows down iPhone 4s, means is the A5 chip powerful enough to handle iOS 8? Like do the heavy games hang in iOS 8 on iPhone 4s?

It doesn't take up much space and actually made my iPhone 4s faster. You can install it now if you register your device's UDID with a developer account through a site like http://www.udid.in/. It's $5, and then you can try iOS 8 before everyone else.