Yes it starts automatically. It is a service not an application. You can open task manager and go to the services tab. There you will see expresscache and it should say running or started. Additionally you can open the GUI. Open your program list and find expresscache. Here you can look at the cache monitor to view usage since last boot.
AS far as performance. You can download a free program called bootracer. This will time your boots. To test it you can open the expresscache GUI and uncheck the enable cache box. Next run bootracer and it will reboot the PC and time it. After you set a baseline for your boot time with out cache then go back and enable the cache and run bootracer again. You should see an improvement.
Keep in mind that performance boost will be dependent on what kind of hardware your PC has. If you have SATA 1 for example the SSD will function at that much slower speed and your performance will not be nearly as much. Same for SATA 2. To get the most out of the Readycache device your PC will need to have SATA 3.
Another factor that can affect performance is what you have loading at startup. If you have a clean PC with no programs loading at startup the performance boost will be less than what you would see on a computer that is loading several programs at start up. This is simply because the less that needs to load the less of the performance you can boost.