Bluetooth 4.1 mainly offers usability updates. One of the most important updates is to allow Bluetooth LE and LTE radios to coexist better. This update allows the radios to coordinate transmissions to decrease the chance of interference. It also makes the data transfer more efficient and allows for better reconnections after connection loss.
The big non-usability change with Bluetooth 4.1 allowed a device to be both a peripheral and a central at the same time.