Hi
I think your zoom feature is a great asset but find that with a lap-top it is very difficult to move the slider in anything like an accurate way. The jumps happen just too quickly particularly at the lower end of the magnification ...which is mostly where we need it. Ideally I would prefer both a user-defined box to enter what magnification I require (which I could "inch" up and down using the up and down arrows as happens in Photoshop boxes) as well as an easier (probably drop-down) scale of pre-defined magnifications. Your slider as is currently configured is just too sensitive for use on a lap-top. Speaking personally I would also prefer percentage quotients to your numeric ones but that is a personal nicety.
Let me know what you think
Best wishes
Stephen