I'll move my ~$100K emergency fund into there just to get free money. And move it out somewhere else when the rates change. Over the years I've moved accounts between Dollar Savings, Emigrant, Orange, Ally, and probably 2 or 3 others...
Would you really move your emergency funds into a less secure more likely problematic service though?
I would have to read up on the transfer times. If it's reasonably standard (2-3 days) and doesn't have any daily limits, then yes. It's a US company, FINRA approved, SIPC insured, so the risk is minimal.
SIPC says they don't think they have to insure this.