I've only broken a suspension line once...and it gave me some warning, but there is absolutely nothing you can do! Nothing to hold on too, no way to brace for impact. So, para-cord or 550 has been banned from my life.
My Hennessey's all have Spectra and have never shown any sign of wear or stress. My home-made hammocks are plain old nylon braid and work great. Not the lightest in the world but it's functional. In sailing, I've found Amsteel to hold knots just fine if you use the right knots. I'll be replacing the nylon braid with it someday.