Yes! I have been using it too. Aside from knowing if your player has been capped, it also has other features like knowing the right price for your arena (or how many you should expand), future salary of your player, the tactics that your opponent has been using for specific game types, the lineup you should use according to your selected preferences like "Inside", "Balanced", etc.
You can set your Access key by clicking the "Preferences" link in the Long Menu.