From a fairly inaccurate sample, I'm seeing ~30k of these per day aimed at a potential target window 64 IPv4 dest-addresses wide. Based on a 30 s traffic capture early in the morning. Things might well be hotter in the middle of the day though, so this could be an underestimate for all I know.
Nothing at all on IPv6, that is, aimed at my IPv6 /64 for this LAN. (I have a /48, but I didn't monitor the whole of that.)
If anyone is interested, I'll put the whole traffic capture up (from a .pcap).