In reply to ffati:
The sling? No. If the rope's not gonna cut, nor is a sling.
That said, I do usually double it over (and I may back it up if I can't double it over, but this is mainly for nervous partners!).
Slings are bomber in the same way rope is as far as I'm concerned. Regular inspection of both is advisable.
Edit: there may be blocks so sharp that I wouldn't trust a rope *or* sling, of course.
Post edited at 13:48