Sorry for being brief earlier, I was heading out the door.
Slipperiness is one thing, but it's fairly minor.
The low melting point means where the rope doubles over the other side making the choker will melt when it gets shock loaded, regardless of how tight you set it. A cow hitch would to the least I believe, but the sling it too short.
The lack of elasticity isn't great, but, IMO, it doesn't matter in slings. The run of rope is so short that even poly doesn't stretch enough to significantly lower peak loads.
If I was set on using it, I'd add a piece of nylon or poly covering to the rope to be put in the bite of the rope to protect it from some melting. A piece on each leg of line would be better, but the practicality wears off.
As the sling gets used it will melt together and be broken apart as it's removed. That adds up to a shorter life than an equivalent cordage with a higher melting point.
The melting equates to the self cutting that Stumpy is talking about.