I've been using them for about two years to attach snatch blocks that guide my continuous line furler. Search eBay for "soft shackle" for the best prices. I have spare lengths of Dyneema but buy them because they're so cheap, and it would be time-consuming to make them.

A good use for them would be to attach a snatch block to a rail, or connect 2 standard blocks back-to-back for a barberhaul, such as this setup.

I use the Holt Allen 40mm blocks below (with the soft shackles looped around the rail stantions and other eyes) to guide my continuous line furler back to the cockpit.