I have been working with my Surface Pro in the dock all day, so I can't attest to battery life, but there's a simple way to figure it out by running a battery report. Open a command window (hit windows-x and select command prompt from the menu) and enter:
powercfg -batteryreport
A HTML report will be generated and posted in your user folder. This will show you battery drains for the last 3 days, so you can compare before and after update. It will also show you how much of your original battery life remains after a full charge, and how long you could expect to have available on a single charge.
As for "fastness," do you mean boot speed or processing speed? I hadn't noticed any difference really...