Is a slight temperature improvement worth voiding the warranty ?

Delidding is a process where you remove the top layer of a CPU, called the integrated heat spreader (IHS). The IHS is a metal plate that sits on top of the actual processing unit (the die) and helps dissipate heat. People delid their CPUs for one main reason: to improve cooling. Please note that it's very risky, and we don't recommend it. Thermal Grizzly launches the Intel High Performance Heatspreader V1. The nickel-plated copper heat spreader has a 207% larger surface area and can reduce temperatures by almost 15°C compared to the stock IHS.

Source: Tom's Hardware