Dell did take time. So it can't be that urgent. I will be waiting at least six months before risking this BIOS update. I thought Microsoft had this vulnerability covered anyway.
I updated my E6430s to the latest bios ( A20 ) about a week ago and everything is good, no issues whatsoever. I also own an E6430 which was also updated to the latest bios (A22) without a hitch. Kudos to the Dell team.
And by the way I have not noticed any performance hit on either laptop.