Definitely with Hussein on this. I have various police Roadcraft training and IAM, and the benefits to using the handbrake are as follows:

Reduction of whiplash injuries if your car is rear-ended as car will not accelerate as fast when hit
Reduction in knock-on collisons if your car is rear-ended
Reduction in accidents from drivers accidentally letting their foot slip off the brake pedal
Reduction in wear to the clutch as even when it is held in, there is incremental drag
Reduction in brake light glare for the driver in front
Shorter pull-away time, as your engine can be at optimum revs before releasing the brake
Less leg strain - long periods in stop go traffic where the left leg is always pressing the pedal result in reduced blood flow and in extreme cases can lead to or exacerbate DVT

There were others as well, but I can't remember them all. These ones make it obvious to me why using the handbrake is a positive benefit.