Increasing the glideslope at an airport purely for noise, in fact for anything for anything other than terrain, shows that the airport is not putting safety first. Pilots all know that an increased glideslope is more demanding, especially in a light headwind, and will increase the workload. Increased workload can lead to increased errors. This is nothing more than LHR trying to appease residents at the expense of flight safety.
The trail will probably prove a success because crew wont accept the steeper approach if the HWC is insufficient, on a training flight, marginal conditions, when fatigue levels are elevated etc, so the results in optimum conditions will look OK.
As MCDU2 says the crew will have to compensate by using high drag techniques which are high noise and you can kiss drag reduction techniques like Flap 3 goodbye.
Very poor show by LHR. Let us hope that other airports do not follow suit and 3.2deg does not become the new norm.