Also, although you've probably already been through this before (& with apologies to those who have). Slave, why do you call it a death leash and what is your alternative?.
I am of the view that most of the time the safety (death) leash allows you to recover the kite after releasing the chicken loop or losing the bar when unhooked. It is connected to only one of your front lines (on a four line kite) depowering the kite. Once or twice my lines have twisted after death looping and I have had to release the safety, but the rest of the time the safety leash system has worked for me.
Although i don't fully agree, Waveslave has a valid point. Personally I use a leash connected suicide style, as i have my loop pop off every now and again and it saves a runaway kite, but sometimes if the swell is really big i'll leave my leash off.
The two major downsides i see are: 1) if you're in real trouble, you have to pull two quick releases not just one. Pulling the leash one can be hard if you're being dragged underwater by a wave, as often you will be getting pulled backwards and can't reach behind your back. 2) the leash can wrap around the end of your bar and pull you into a death loop. I've had this happen once.