Grok Bot blew $650 in BigQuery when analyzing something trivial that I shouldn't really care about (going through a giant speedtest table, looking for a New Zealand ISP with the best international performance). It then wrote a nice letter of appeal so Google refunded this to me.

Otherwise I've been pretty happy with it. It's been absolute blast with Home Assistant and OpenWRT (tightening up network security and cutting off iot devices from WAN).